UNIVERSITY  OF  CALIFORNIA.; 

FROM   THE    LIBRARY   OF 

DR.  JOSEPH    LeCONTE. 

GIFT  OF  MRS.   LECONTE. 
No. 


I 


km 


1  *fcli 


i? 


9, 


ELEMENTARY  SCIENCES 


CHAMBERS'     EDUCATIONAL    COURSE 

NUMBER   Til. 


ELEMENTS 


OF 


GEOLOGY, 


BY    DAVID    PAGE. 


EDITED  BY  D.  M.  REESE,  M.  D.,  LL.  D. 


NEW-YORK: 

PUBLISHED    BY    A.    S.  BARNES    &    CO, 
PHILADELPHIA:    JOHN  BALL. 
H.   W.  DERBY   &  CO. 

CINCINNATI. 

1849. 


CHAMBERS'  EDUCATIONAL  COURSE. 


Tlif>  object  of  the  following  works  is  to  furnish  the  friends  of  HU  improved 
system  of  education  with  the  hooks  required  fur  carrying  out  their  views,  in 
the  actual  business  of  the  school-room,  and  the  family  circle. 

The  Messrs.  Chambers  (whose  works  are  so  favorably  known  in  the  different 
departments  of  literature,  throughout  this  country  as  well  as  Europe)  have 
employed  the  first  professors  in  Scotland  in  the  preparation  of  these  works. 
They  are  now  offered  to  the  schools  of  the  United  States,  under  the  American 
revision  of  D.  M.  REKSE,  M.  D..  LL.  D.,  late  superintendent  of  public  schools 
of  the  city  and  county  of  New-  York. 


I.—  CHAMBERS'      TR  E  ASUR  Y  OF  K  NOWLEDG  E.     (3  parts  in  one.) 

BY  W.  &  R.  CHAMBERS. 

PART  1  Embrace)  Elementary  Lessons  in  Gammon  Things—  or  things  which  lie  most  imme 
diately  around  us,  and  first  attract  the  attention  of  the  young  mind.  PART  -I  Embrace 
Practical  Lessons  on  Common  Objects—  such  as  articles  or  objects  from  the  Mineral.  Vege 
table,  and  Animal  Kingdoms,  manufactured  articles,  miscellaneous  substances  and  objects,  &c 
PART  3  Embraces  Introduction  to  the  Sciences.  This  presents  a  systematic  view  of  nature 
under  the  various  sciences.  Care  is  taken  that  the  information  given  should  not  be  a 
superficial  view  of  a  lew  unconnected  phenomena,  but  a  chain  of  principles  calculated,  in 
combination,  to  impress  a  distinct  and  comprehensive  idea  to  the  mind  of  the  very  young  child 

This  volume  is  designed  for  an  early  reading  book,  that  the  scholar  may  be  exercised  in  reading. 
and  at  the  same  time  acquire  knowledge  of  such  subjects  as  his  capacity  will  enable  him  t« 
understand.  It  contains  much  useful  information  upon  common  objects  of  life. 

II.—  CHAMBERS'      E  LF  M  E  NTS  OF   DR  AWI  NG.     (2  parts  in  one.) 

BY  JOHN  CLARK. 

PART  1  Embraces  Exercises,  for  the  Slate.  PART  -2  Embrace!  the  Principle}  of  Drawing 
and  Perspective. 

With  but  very  few  exceptions,  children  are  fond  of  making  efforts  in  Drawing.  Furnished  with 
a  black-lead  pencil  and  sheet  of  paper,  or  slate  and  pencil,  they  are  delighted  to  scribble 
whatever  their  fancy  suggests.  Followed  up  methodically  by  the  teacher,  their  infant 
aspirations  may  lead  to  the  development  of  much  valuable  talent.  Illustrated  by  Engravings. 

III.—  CHAMBERS'      ELEMENTS  OF   NATURAL   PHILOSOPHY. 

THREE  PARTS  IX  ONE. 

PART  1  Embraces  Laws  of  Matter  and    M'>fi'>n.     PART  2  Embrace)   Mechanic).    PART  3 

Embraces  Hydrostatics,  'Hy  Iraulics,  and  Pneumatics. 
In  the  treatment  of  the  several  subjects  great  care  has  been  taken  to  render  the  language  simple 

and  intelligible.    Illustrated  by  '  Wood  Engravings- 

IV  —CHAMBERS'      CHEMISTRY   AND   ELECTRICITY. 

PART  1  Embraces  Illustrations.  and  experiments  of  the  Chemical  Phenomena  of  Daily  Life. 
By  D.  B.  REID,  M.  D.,  F.  R.  S.  E.  PART  -1  Embraces  Electricity,  (statical  and  current.) 
By  ALEXANDER  BAIN,  the  original  inventor  of  Electric  and  Telegraphic  clocks. 

This  work  is  designed  to  facilitate  the  introduction  of  Chemistry  as  an  elementary  branch  oj 
education  in  schools.  Illustrated  by  Engravings. 

V.—  CHAMBERS'      VEGETABLE    AND   ANIMAL   PHYSIOLOGY. 

BY  O.  HAMILTON,  M.  D. 

PART  1  Embraces  the  General  Structure  and  Functions  of  Plant*.    PART  2  Embraces  tht 

Organization  of  Animals. 
The  object  of  this  work  is  to  unite  Vegetable  and  Animal  Physiology,  and  bring  both  systems 

under  one  head,  as  properly  connected  and  adapted  to  the  mind  of  the  student. 

VI  —CHAMBERS'      ELEMENTS  OF  ZOOLOGY.     (Illustrated;, 

Presenting  a  complete  view  of  the  Animal  Kingdom  as  a  portion  of  external  nature.  As  the 
composition  of  one  of  the  most  eminent  physiologists  of  our  age,  it  possesses  an  authority  not 
attributable  to  such  treatises  in  general. 

VII.—  CHAMBERS'      E  LE  M  E  NTS  OF  GEOLOGY.     (Illustrated.) 

BY  DAVID   PAGE. 

The  subject  is  here  presented  in  its  two  aspects  of  interesting  and  important.  Interesting, 
inasmuch  as  it  exhibits  the  progressive  conditions  of  the  earth  from  the  remotest  periods,  and 
reveals  the  character  of  the  plants  and  animals  which  have  successively  adorned  and  peopled 
its  surface  ;  and  important,  as  it  determines  the  position  of  those  metals  and  minerals  upon 
•which  the  arts  and  manufactures  so  intimately  depend. 


Entered 

.  S.  BARNES  &  CO., 
in  the  Clerk>»  Office  of  the  District  Court  of  the  Southern  District  of  New- York. 


i 


Q 


\o 


INTRODUCTORY  OBSERVATIONS, 


THE  AMERICAN  EDITOR. 

ss  

IT  is  only  within  the  present  century,  that  the  subject  of 
this  volume  has  been  recognised  as  a  science,  and  hence  not- 
withstanding the  ardour  with  which  it  has  been  cultivated, 
and  the  rapid  advances  it  has  made,  it  must  still  be  considered 
in  its  infancy.  There  are  two  objects  included  in  the  inves- 
tigations of  this  science,  viz.:  1.  The  present  condition  of 
the  earth's  surface;  and  2.  The  changes  to  which  it  has 
been  subjected.  The  former  may  be  called  positive  geology, 
and  imbodies  the  facts  of  the  science;  the  latter  is  speculative 
geology,  and  includes  the  theories  which  are  proposed  to 
explain  and  account  for  the  changes  which  have  occurred  in 
the  structure  of  the  globe  during  past  ages.  Hence  it  has 
been  proposed  to  call  the  former  geognosy,  including  our 
absolute  knowledge ;  and  the  latter  geology,  comprising  spe- 
culative reasoning;  but  as  they  are  jointly  cultivated,  the 
latter  term  is  employed  to  embrace  both,  and  has  been  very 
generally  adopted. 

Of  the  certainty  which  attaches  to  much  of  the  speculative 
department  of  geology,  and  of  its  claims  to  the  character  of 
an  inductive  science,  and  the  comparative  rank  to  which  it  is 
entitled,  there  is  still  a  diversity  of  opinion  among  philoso- 
phers. Sir  John  Herschel,  however,  in  view  of  its  recent 
developments  has  declared  his  opinion  that  in  point  of  dignity 
and  the  extensive  range  of  its  subjects,  it  deservedly  ranks 


101296 


VI  INTRODUCTORY  OBSERVATIONS. 

second  to  astronomy.  This  is  certainly  high  praise,  and  from 
great  authority.  Indeed,  the  facts  of  the  science  which  have 
been  already  established,  and  which  are  rapidly  accumulating, 
are  of  themselves  full  of  interest,  and  many  of  them  of  the 
highest  practical  importance.  The  speculative  reasoning  on 
these  facts  may  or  may  not  be  worthy  of  equal  confidence; 
but  very  much  of  it  will  be  found  to  be  rational  and  satisfac- 
tory, and  will  continue  to  be  held  in  high  esteem  until  some 
better  solution  shall  be  given  to  the  problems,  which  the 
absence  of  historical  or  geological  records  have  left  unex- 
plained. 

But  with  the  facts  of  the  science  we  have  chiefly  to  do  in 
this  elementary  volume,  and  the  author  has  presented  these 
in  a  form  of  simplicity  and  attractiveness  which  admirably 
adapts  the  subject  to  the  young,  rendering  it  a  most  agreeable 
and  useful  study.  The  latest  discoveries  are  here  stated,  and 
very  little  improvement  of  the  text  has  been  called  for  by  the 
editor,  who  has  contented  himself  mainly  by  the  adaptation 
of  analytical  questions  which  will  be  found  on  every  page, 
and  it  is  hoped  will  be  useful  both  to  the  teachers  and  the 
pupils  of  those  schools  in  which  this  work  may  be  intro- 
duced. 

In  a  science  so  new,  and  with  a  nomenclature  not  yet  per- 
fected, it  has  been  obviously  impracticable  to  dispense  with 
the  technicalities  of  the  science ;  for  the  most  of  which, 
indeed,  there  are  neither  substitutes  nor  synonymes  in  our 
language.  They  will  all  be  found  accompanied  by  explana- 
tory notes  at  the  end  of  each  section  in  which  they  first  occur, 
and  which  render  them  perfectly  intelligible. 

In  using  this  book  in  schools,  it  is  recommended  that  each 
section  be  made  a  lesson  for  study  and  recitation.  The  read- 
ing of  each  paragraph  to  be  followed  by  proposing  the  ques- 
tions in  the  order  they  are  numbered,  an  answer  being  required 
in  the  language  of  the  book ;  and  afterwards,  if  need  t>e,  in 
other  terms,  and  accompanied  by  other  illustrations  when 
practicable.  In  the  speculative  department,  touching  the 


INTRODUCTORY    OBSERVATIONS.  Vll 

periods  and  eras  of  past  ages,  and  the  chronological  hypo- 
theses which  are  hazarded,  may  be  made  the  topic  of  collo- 
quial and  familiar  conversation,  or  of  an  oral  lecture. 

In  this  way,  it  is  confidently  believed  that  a  very  good 
knowledge  of  this  new  science  and  its  important  practical 
and  economical  uses  may  be  readily  imparted.  And  in  its 
adaptation  to  the  use  of  schools,  there  can  be  little  doubt  that 
among  practical  teachers,  this  volume  will  be  esteemed  to 
possess  very  superior  advantages.  As  such  it  is  recom- 
mended to  public  favour.  D.  M.  R. 


PREFACE. 


GEOLOGY,  in  its  aim  to  describe  the  materials  composing 
the  earth's  crust,  their  mode  of  arrangement,  and  the  causes 
which  seem  to  have  produced  that  arrangement,  constitutes 
one  of  the  most  interesting  and  important  of  the  natural  sci- 
ences. Interesting,  inasmuch  as  it  exhibits  the  progressive 
conditions  of  the  world  from  the  remotest  periods,  and  reveals 
the  character  of  the  plants  and  animals  which  have  succes- 
sively adorned  and  peopled  its  surface ;  and  important,  as  it 
determines  the  position  of  those  metals  and  minerals  upon 
which  the  arts  and  manufactures  so  intimately  depend.  Va- 
luable as  are  its  deductions,  Geology  is  comparatively  of 
recent  growth,  it  being  only  within  the  present  century  that 
accurate  data  have  been  collected,  and  those  absurd  specula- 
tions respecting  the  origin  of  the  globe  eschewed,  which  had 
so  long  impeded  the  legitimate  prosecution  of  the  subject. 
If,  however,  long  repressed  by  the  imprudence  of  its  early 
cultivators,  no  branch  of  human  knowledge  has  made  more 
rapid  progress  since  right  modes  of  investigation  were  adopted 
— none  attracted  a  greater  degree  of  attention,  or  been  more 
generally  applicable  to  the  economical  purposes  of  life.  To 
furnish  an  outline  of  the  science  in  its  present  state  of  ad- 
vancement is  the  object  of  the  following  treatise,  in  which 
the  leading  facts  are  stated  in  as  simple  a  manner  as  is  con- 
sistent with  accuracy.  Technical  terms,  often  so  ignorantly 
inveighed  against,  have  not  been  avoided,  but  have  been  gra- 
dually introduced  with  their  explanations,  to  familiarize  the 
learner  with  Geological  language,  and  thus  prepare  him  for 
the  study  of  more  advanced  works,  as  well  as  for  the  prac- 
1* 


X  PREFACE. 

tical  prosecution  of  the  subject.  A  uniform  arrangement  of 
the  topics  has  been  strictly  adhered  to,  so  as  at  once  to  assist 
the  memory  and  facilitate  reference ;  theoretical  disquisitions 
have  been  studiously  avoided ;  and  a  plain  record  of  facts  and 
observations  presented,  in  order  that  the  treatise  might  answer 
the  end  intended — namely,  for  Use  in  Schools  and  for  Private 
Instruction. 


CONTENTS. 


OBJECTS  OF  GEOLOGY •        .        11 

GENERAL  STRUCTURE  AND  CONDITIONS  OF  THE  GLOBE — 

Figure .  18 

Density  19 

Temperature 20 

Surface  Configuration .  25 

Distribution  of  Land  and  Water 26 

,  Constitution  of  the  Ocean 29 

The  Atmosphere 31 

Planetary  Relations          ....*..  32 

CAUSES  MODIFYING  THE  STRUCTURE  &  CONDITIONS  OF  THE  GLOBE — 

Atmospheric  Agencies  36 

Aqueous  Agencies 44 

Igneous  Agencies  52 

Organic  Agencies          ........    59 

Recapitulation  of  Modifying  Causes          ....        65 

MINERAL  SUBSTANCES  COMPOSING  THE  EARTH'S  CRUST  .    66 

MEANS  OF  GEOLOGICAL  INVESTIGATION           .       ...  73 

Forms  of  Stratification         .        .        .        .  *     .        •  .    76 

Positions  of  Unstratified  Rocks 78 

ORYCTOLOGY— .SCIENQE  OF  FOSSILS  • .     .       .        .       .80 

Petrifaction,  Bituminization,  Metallization  ...  81 
Fossil  Botany  and  Zoology  .  •  •  •  .  .84 

CLASSIFICATION  OF  ROCK  FORMATIONS  ....       .       88 

Table  of  British  Deposits  .*• 90 

Section  of  Existing  Arrangement  of  Rocks  .        .        94 

GRANITIC  BASIS  OF  PRIMARY  STRATA  *  .  .  .  .  97 
GNEISS  AND  MICA  SCHIST  SYSTEMS  >'•*,«  .  .  101 
CLAY-SLATE,  GRAUWACKE,  AND  SILURIAN  SYSTEMS  .  .  108 

OLD  RED  SANDSTONE  SYSTEM  .  . "  •  ,  •  •  •  *21 
Classification  of  Fossil  Fishes  '>.  ".*'..  .130 

CARBONIFEROUS  SYSTEM  .  ' 134 

Mountain  Limestone  .  .  .  .  .  •'  .  .  .  .  135 
Coal  Measures  ».  •  ." 141 


Xll  CONTENTS. 

Page 
NEW  RED  SANDSTONE  SYSTEM 158 

OOLITIC  SYSTEM — 

Lias,  Oolite,  and  Wealden  Groups 166 

CKETACEOUS  OR  CHALK  SYSTEM 179 

TERTIARY  STRATA 186 

SUPERFICIAL  ACCUMULATIONS          ..'...       198 

Erratic  Block,  or  Boulder  Group 201 

Ossiferous  Sands  and  Gravel    ......       205 

Ossiferous  Caves,  Fissures,  and  Breccia      ....  208 

Raised  Beaches — Submarine  Forests        .        .        .        .211 

Marine  Silt,  Sand-drift,  Shingle  Beaches,  &,c.    .        .        .  215 

Submarine  Deposits  and  Accumulations  .         .         .       218 

Terraces  in  Valleys 219 

Deposits  in  Valleys 221 

Deltas  and  Estuary  Deposits         ......  222 

Lacustrine,  or  Lake  Deposits   ......       228 

Chemical  and  Mineral  Deposits 231 

Peat-Mosses,  Jungle,  Vegetable  Drift      .         .         .         .235 
Shell-Beds,  Coral- Reels,  "&c.      ..'...  242 

Soils 251 

Earthquakes  and  Volcanoes 254 

RECAPITULATION  OF  THE  STRATIFIED  SYSTEMS        .        .        .      262 
IMPORTANCE  OF  GEOLOGICAL  SCIENCE  .  274 


GEOGRAPHICAL  GEOLOGY. 

ASIA        .        . 281 

AFRICA 289 

EUROPE t  292 

NORTH  AMERICA 300 

SOUTH  AMERICA       .        .        .        .        .        .        t  §18 

APPENDK 323 

INDEX      ......  .  827 


ORYCTOLOGICAL   CHART. 


„      I   I '   1)M> 

3-       OrtliocerciUtes 


£-|     p>v,^sc_-      f:  ^_ .L^r: 


The  aeological  Distribution  of  Fossil  Organic  Remains. 


THE  ORYCTOLOGICAL  CHART.  —  This  is  a  representation  of  the 
leading  facts  in  Oryctology,  exhibiting  all  the  important  organic 
remains  of  the  different  formations.  The  greater  or  less  space  occu- 
pied by  the  various  tribes  of  animals  and  plants  on  the  chart  shows 
their  comparative  abundance  or  paucity.  The  branches  designate 
the  species.  When  one  entirely  disappears  during  some  formation, 
but  afterward  reappears,  a  line  is  drawn  where  it  is  wanting.  The 
whole  brings  under  a  glance  of  the  eye  the  rise,  developement,  rami- 
fication, and  extirpation  of  the  different  tribes. 


GEOLOGY. 


OBJECTS   OF  GEOLOGY. 

1.  GEOLOGY  is  that  science  which  treats  of  the  mate- 
rials composing  the  earth's  crust,  their  mode  of  arrange- 
ment, and  the  causes  which  seem  to  have  produced  that 
arrangement.     (See  Appendix.) 

2.  By  the  earth's  crust  is  meant  that  external  shell  or 
covering  of  solid  matter  which  is  accessible  to  man's  inves- 
tigation.    The  highest  mountains  do  not  rise  five  miles 
above  the  level  of  the  sea,  and  the  deepest  mines  descend 
only  about  a  third  part  of  a  mile,  so  that,  even  were  we 
perfectly  acquainted  with  the  entire  space  between  the  top 
of  the  highest  mountain  and  the  bottom  of  the  deepest 
mine,  it  would  form  but  a  very  insignificant  fraction  of 
the  distance  between  the  surface  and  centre  of  the  globe, 
which  is  nearly  4000  miles.     Thin  as  this  crust  may  seem, 
it  nevertheless  presents  innumerable  objects  for  investiga- 
tion ;  hence  the  magnitude  of  this  science,  which  has  been 
ranked,  in  point   of  importance,  second  only  to  that  of 
astronomy. 

3.  The  materials  which  compose  the  crust  of  the  globe  are 
exceedingly  varied.     For  instance,  one  part  of  the  surface 
is  covered  with  sand,  another  with  clay,  and  a  third  with 
gravel.     How  were  these  materials  formed,  whence  were 
they  derived,  and  by  what  agency  were  they  laid  down  in 

1.  Define  Geology. 

2.  What  is  the  earth's  crust  1 

3.  What  of  the  highest  mountains,  and  deepest  mines  ? 

4.  What  of  the  semi-diameter  of  the  earth  f 
6.  How  does  the  surface  of  the  earth  vary  f 


1*2  GF.OLOGY. 

their  present  position?  Again,  shells  and  bones  may  be 
found  in  the  sand  arid  clay,  plants  and  trees  in  the  peat- 
earth.  How  came  these  remains  to  be  buried  there,  and 
are  they  similar  to  those  animals  and  vegetables  now  living 
arid  growing  upon  the  earth?  As  we  dig  through  the 
sands,  gravels,  and  clays,  we  come  upon  rocks,  some  in 
layers,  others  in  masses;  some  are  hard  and  sparkling, 
others  soft  and  earthy;  and  most  of  them  differ  in  colour. 
Many  of  them  differ  also  in  the  kind  of  matter  of  which 
they  are  composed,  such  as  sandstone,  limestone,  coal, 
roofing-slate,  &c.  How  were  these  rocks  formed,  and  by 
what  means  were  they  laid  down  in  their  present  positions? 
for  rocks  so  different  in  kind  as  limestone,  coal,  and  sand- 
stone, must  have  been  formed  under  different  circumstances. 
Further,  we  find  petrified  shells,  fishes,  bones,  and  plants 
imbedded  in  these  rocks;  and  different  rocks  contain  dif- 
ferent kinds  of  these  remains.  How  were  they  imbedded 
there?  Are  they  similar  to  shells,  fishes,  and  plants  now 
existing?  Do  they  seem  to  have  lived  and  grown  in  the 
sea,  in  fresh  water,  or  on  dry  land  ?  Such  are  a  few  of 
the  questions  which  it  is  the  province  of  the  geologist  to 
consider;  and  in  doing  so,  he  must  ground  his  reasoning 
upon  the  analogy  of  the  changes  now  going  forward  on  the 
face  of  the  globe,  endeavouring  to  discover  what  relation 
they  bear  to  former  changes,  and  whether  both  may  be 
ascribed  to  similar  causes. 

4.  The  causes  which  modify  the  crust  of  the  globe  are 
very  numerous,  differing  in  power,  as  well  as  in  their  mode 
of  action.  At  present  we  find  rivers  bearing  down  mud, 
sand,  and  gravel,  and  depositing  the  same  either  along  their 
banks,  in  lakes,  or  in  the  sea — these  deposits  form  ing  layers 
of  mud,  sand,  or  gravel,  which  in  some  cases  become  con- 
solidated, and  assume  a  rocky  appearance.  If  plants,  shells, 


fo.  What  else  is  found  under  these  materials  ? 

7.  What  variety  in  these  rocks  ? 

8.  What  is  imbedded  in  many  rocks  ? 

9.  What  questions,  and  how  solved  ? 

10.  What  of  rivers  and  their  deposits  ? 

11.  What  of  rains,  frosts,  winds,  &c.  ? 

12.  How  do  plants  and  animals  modify  the  earth's  crust 1 


OBJECTS    OF    GEOLOGY.  13 

or  dead  animals  be  carried  down  at  the  same  time  by  these 
rivers,  they  will  be  imbedded  in  the  layers  so  formed,  and 
will  in  course  of  time  become  petrified,  or  converted  into 
stony  matter.  Rains,  frosts,  winds,  and  the  like,  act  upon 
all  rocks,  and  make  them  crumble  down,  thus  leaving  the 
decayed  matter  to  form  additional  surface  soil,  or  to  be 
borne  down  by  rivers  and  other  currents  of  water.  Plants 
and  animals  also  modify  the  crust  of  the  globe :  plants  grow 
and  decay,  either  adding  matter  to  the  soil,  or  forming 
accumulations  in  marshes,  in  the  character  of  peat-moss : 
animals  also  yield  their  remains  to  the  surface ;  and  some 
of  them,  as  shell-fish  and  corals,  form  vast  accumulations 
of  solid  matter.  Earthquakes  break  up  the  earth's  crust, 
elevating  some  places,  and  sinking  others ;  raising  the  bot- 
tom of  the  sea  to  become  dry  land,  and  sinking  dry  land 
under  the  ocean.  Volcanoes  are  sometimes  accompanied 
with  similar  effects,  and  generally  throw  out  liquid  lava, 
which,  when  cooled  down,  forms  rocks ;  and  repetitions  of 
these  discharges  gradually  form  mountains. 

[In  this  general  summary  of  the  causes  which  modify  the 
crust  of  the  globe,  no  reference  is  made  to  the  geological 
agency  of  man,  and  that  of  animals  in  general  is  but 
slightly  alluded  to.  "By  the  destruction  of  animals;  by 
the  distribution  of  both  plants  and  animals ;  by  altering  the 
climate  of  large  tracts  of  country  by  means  of  cultivation  ; 
by  resisting  the  encroachments  of  rivers  and  of  the  ocean  ; 
by  reducing  hills  and  mountains ;  by  furnishing  the  spoils 
of  his  own  power,  and  of  the  products  of  his  art,  to  make 
up  portions  of  soil ;  man  has  exerted  no  small  influence  in 
changing  the  earth's  surface."  But  in  the  language  of  the 
author  of  the  "Wonders  of  Geology,"  the  labours  of  the 
human  race,  in  a  geological  view,  sink  into  utter  insignifi- 
cance, when  compared  with  the  achievements  of  animals 
invisible  to  the  naked  eye, — of  beings  which  live,  flourish, 
and  die  without  the  notice  of  the  lord  of  creation.  Of  the 
geological  agency  of  various  kinds  of  animals,  the  same 
author  names  the  following,  viz : — "  The  infusoria  in  the 


13.  What  of  earthquakes  ? 

14.  What  changes  are  produced  by  volcanoes  1 


14  GEOLOGY. 

formation  of  immense  beds  of  marl;  the  polyparia  in 
the  creation  of  vast  coral  islands;  marine  and  fresh  water 
shell-fish,  in  producing  the  beds  of  limestone,  which  are 
supposed  to  constitute  one-seventh  part  of  the  crust  of  the 
globe;  the  shells,  reptiles,  and  fishes  which  have  formed 
various  kinds  of  marble;  the  corals,  sponges,  and  radiata 
that  have  formed  the  beds  of  chalk  and  flint;  and  many 
others  which  have  caused  the  whole  surface  of  our  earth  to 
pass  through  the  wonderful  laboratory  of  life."] 

5.  The  causes  enumerated  in  the  preceding  paragraph  are 
those  which  mainly  contribute  to  the  modification  of  the 
crust  of  the  globe.     In  general  they  act  gently,  and  within 
limited   spaces;  occasionally  with  great  violence,  and  over 
a  large  extent  of  country.     These   forces  have  always  ex- 
erted themselves  with  greater  or  less  intensity,  and  have 
always  produced   corresponding  results.     In  reference  to 
the  masses  of  sand,  gravel,  and  clay,  now  far  removed  from 
waters,  and  to  the  various  rocks  which  are  found  at  great 
depths  in  the  earth's  crust,  it  is  the  object  of  geology  to  dis- 
cover whether  they  are  to  be  ascribed  to  the  operation  of 
forces  similar  in  kind,  but  greater  in   degree,  than  those 
above-described ;  and  whether  the  plants  and  animals  found 
petrified  within   them  be  or  be  not  of  the  same  kinds  as 
those  now  existing.     If  they  are  of  the  same  races,  did 
they  exist  under  similar  circumstances?  and  if  not,  what 
seem  to  have  been  the  conditions  of  the  world  under  which 
they  flourished? 

6.  To  solve  the  numerous  problems  which  geology  thus  em- 
braces, a  vast  amount  of  research  and  knowledge  is  neces- 
sary.    To  account  for  the  aggregation  of  positions  of  many 
rock  masses,  the  geologist  requires  to  be   acquainted  with 
the  principles  of  mechanics ;  to  treat  of  their  composition 
and  formation,  the  aid  of  chemistry  must  be  called  in ;  to 
describe  and  classify  the  remains  of  plants  and  animals,  he 
must  have  recourse  to  botany  and  zoology;  while,  generally 
speaking,  there  are  many  of  his  problems,  for  the  successful 

15.  What  variety  in  the  action  of  these  several  agencies? 

16.  How  does  Geology  investigate  these,  and  for  what  purposes  T 

17.  Which  of  the  natural  sciences  is  in  requisition  here  f 


OBJECTS    OP    GEOLOGY.  15 

solution  of  which  the  assistance  of  almost  every  branch  of 
natural  science  is  necessary.  An  amount  of  acquirements 
so  varied  is  beyond  the  compass  of  many  minds ;  hence 
geology  has  been  divided  into  several  departments,  which, 
while  ultimately  depending  on  each  other  for  their  pro- 
gress, can  be  studied  as  individual  sciences.  These  are — 
Physical  Geography,  which  limits  itself  to  the  mere  sur- 
face and  configuration  of  the  earth  as  occupied  by  land  and 
water,  mountains  and  valleys,  and  other  external  appear- 
ances; Mineralogy,  which  treats  of  the  individual  crystals 
or  minerals  of  which  rock  masses  are  composed;  and 
Oryctology,  or  Paleontology ,  which  directs  itself  exclu- 
sively to  the  consideration  of  the  fossil  plants  and  animals 
that  may  be  discovered  in  the  crust  of  the  globe. 

7.  Abstract  or  speculative  geology  comprehends  all  these 
branches,  and,  were  it  a  perfect  science,  would  present  a 
history  of  the  globe  from  its  origin  and  formation,  through 
all  the  changes  it  has  undergone,  up  to  the  present  time ; 
describing  its  external  appearance,  its  plants  and  animals, 
at  each  successive  period.  As  yet,  geology  is  the  mere 
aim  to  arrive  at  such  knowledge ;  and  when  we  consider 
how  difficult  it  is  to  trace  the  history  of  a  nation  even  over 
a  few  centuries,  we  cannot  be  surprised  at  the  small  pro- 
gress geologists  have  made  in  tracing  the  history  of  the 
earth  through  the  lapse  of  ages.  To  ascertain  the  history 
of  a  nation  possessed  of  written  records,  is  a  task  compara- 
tively easy ;  but  when  these  are  wanting,  we  must  examine 
the  ruins  of  their  cities  and  monuments,  and  judge  of  them 
as  a  people  from  the  size  and  structure  of  their  buildings, 
and  from  the  remains  of  art  found  therein.  This  is  often 
a  difficult,  a'nd  all  but  impracticable  task ;  much  more  so  is 
it  to  decipher  the  earth's  history.  It  is  true  that  certain 
geological  facts  are  recorded;  but  the  record  is  neither  dis- 
tinct nor  of  much  antiquity.  We  learn  that  earthquakes 


18.  Define  Physical  Geology,  Mineralogy,  Oryctology,  &c. 

19.  What  of  the  objects  of  speculative  geology  I 

20.  Why  does  it  fail  to  do  all  this  ? 

21.  How  is  a  nation's  history  studied  ? 

22.  What  geological  records  exist  t 


16  GEOLOGY. 

have  raised  land  above,  or  sunk  it  beneath,  the  sea ;  that 
volcanoes  have  formed  mountains  and  buried  cities,  such  as 
Herculaneum  and  Pompeii;  that  the  mud  of  rivers  has 
formed  vast  plains  like  the  Deltas  of  the  Nile  and  Ganges; 
that  cities  once  on  the  sea-shore  are  now  several  miles 
inland;  and  that  cities  once  removed  from  the  sea  have 
oeen  washed  away  by  its  inroads,  their  sites  now  forming 
the  bed  of  the  ocean.  Beyond  a  few  facts  like  these,  we 
have  no  written  geological  record ;  and,  for  the  earlier  his- 
tory of  the  earth,  must  descend  into  the  gravels,  clays,  and 
rocks  which  form  its  crust ;  judge  of  past  changes  by  the 
character  of  these  masses ;  and  reason  as  to  the  kind  of 
plants  and  animals  which  formerly  peopled  its  surface, 
from  the  petrified  remains  which  are  entombed  in  the  strata 
beneath. 

8.  The  practical  utility  of  geology  is  alike  varied  and 
extensive.  The  metals  so  indispensable  to  the  purposes  of 
civilized  life  are  all  dug  in  the  shape  of  ores  from  the  rocky 
crust,  certain  metals  being  found  in  certain  rocks,  and  in 
certain  positions.  As  with  metals,  so  with  coal,  building- 
stone,  limestone,  and  other  minerals;  and  it  is  the  duty  of 
practical  geology  to  direct  the  miner  in  his  search  for  these 
valuable  metals  and  minerals,  and  to  point  out  to  him  by 
what  means  they  can  be  most  economically  obtained.  In  a 
country  like  ours,  where  railroads,  canals,  reservoirs,  tun- 
nels, and  harbours  are  in  constant  requirement,  the  deduc- 
tions of  geology  must  be  of  first  importance  in  pointing  out 
the  kind  of  rocks  through  which  these  operations  have  to 
be  conducted,  as  also  in  ascertaining  the  strength  and  du- 
rability of  the  building  material  required  by  the  engineer 
and  architect.  Soils  being  in  many  cases  composed  of  the 
decayed  materials,  as  well  as  influenced  by  the  porous  or 
compact  texture  of  the  underlying  rocks,  there  must  sub- 
sist an  intimate  connexion  between  them  ;  an  acquaintance 
with  the  prevalent  characters  of  rock  formations  will,  there- 
fore, greatly  assist  the  agriculturist  in  his  endeavours  to 

23.  How  then  do  our  researches  extend  beyond  these  1 

24.  In  what  is  the  practical  utility  of  geology  seen  1 

25.  What  of  great  public  works,  and  buildings  ? 

26.  How  is  it  important  to  the  agriculture  of  the  country? 


OBJECTS    OF    GKOLOOIT.  17 

improve  the  fertility  of  the  soil.  Other  practical  advantages 
to  be  derived  from  the  study  of  geology  might  be  pointed 
out :  but  these  will  be  best  considered  in  a  subsequent  part 
of  the  treatise,  when,  as  may  be  supposed,  the  student  will 
be  better  able  to  judge  of  their  importance. 

i.  EXPLANATORY  NOTE. 

GEOLOGY  (Greek,  ge,  the  earth,  and  logos,  a  discourse) — reasoning 
about  the  structure  of  the  earth.  The  term  Geognosy  (from  ge,  and 
gnosis,  knowledge)  is  sometimes  used  instead  of  geology,  the  former 
signifying  absolute  knowledge,  and  the  latter  implying  speculative 
reasoning.  Geology,  however,  is  the  term  most  frequently  in  use,  and 
is  likely  to  continue  so. 

CRUST — the  outer  or  solid  covering  of  any  body,  such  as  the  crust  of 
a  loaf,  the  shell  of  an  egg,  &c.  The  crust  generally  differs  in  quality 
from  the  internal  parts,  which  it  covers  ;  hence  the  term  "  crust  of  the 
earth"  is  used  to  distinguish  it  from  the  interior  of  the  globe,  concerning 
which  we  have  no  certain  knowledge. 

PETRIFIED,  PETRIFACTIONS  (Latin,  pet ra,  a  stone,  and  facere,  to  make) 
— to  make  or  change  into  stone.  When  a  shell,  bone,  or  piece  of  plant, 
by  being  enclosed  in  rocky  matter,  becomes  hard  and  heavy  like  stone, 
yet  retains  its  shape,  it  is  said  to  be  petrified.  Petrification  is  thus 
caused  by  the  particles  of  stony  matter  entering  into,  and  filling  the 
pores  of  the  animal  or  vegetable  structure  ;  lime-water,  for  instance, 
entering  int6  the  pores,  and  between  the  fibres  of  a  piece  of  wood, 
makes  it  a  limy  petrifaction. 

FOSSIL  (Lat.,  fossus,  dug  up) — anything  dug  up  out  of  the  earth  is 
fossil ;  but  the  term  "  fossils,"  or  "  fossil  remains  "  is  now  generally 
applied  to  petrified  vegetable  or  animal  remains  dug  out  of  the  earth's 
crust. 

ORYCTOLOGY  (Gr.,  orusso,  to  dig,  and  logos,  a  discourse) — a  discourse 
or  reasoning  about  things  dug  up.  PALEONTOLOGY  (from  palaios, 
ancient,  on/a,  beings,  logos,  a  discourse) — a  discourse  or  reasoning  about 
ancient  beings.  Both  of  these  terms  are  used  by  geogolists  to  signify 
the  science  of  fossil  remains  ;  some  objecting  to  oryctology  as  merely 
referring  to  things  dug  up,  while  common  stones  are  dug  up  as  well  as 
remains  of  plants  and  animals  ;  others  objecting  to  palaeontology,  be- 
cause, though  it  refers  to  ancient  beings,  it  does  not  imply  that  they  are 
fossil. 

STRATUM,  plural  STRATA  (Lat.,  stratus,  strewn,  or  spread  out).  When 
different  rocks  lie  in  succession  upon  each  other,  each  individual  forms 

27.  Define  Geognosy,  as  distinguished  from  Geology. 

28.  How  is  the  crust  of  the  earth  illustrated  ? 

29.  From  what  is  it  contradistinguished,  and  why  1 

30.  Define  petrifaction,  and  explain  by  example. 

31.  What  is  understood  by  fossils  ? 

32.  Distinguish  Oryctology  from  Palaeontology. 

33.  What  objections  to  these  terms  ? 

34.  Define  stratum,  stratified,  &c. 


18  GEOLOGY. 

a  stratum;  and  is  so  termed  from  its  appearing  to  have  been  laid,  or 
npread  out  in  order.  Rocks  arranged  in  parallel  layers  are  thus  said  to 
be  stratified  ;  and  those  among  which  there  is  no  appearance  of  this 
parallel  arrangement,  unstratified. 

GENERAL  STRUCTURE  AND  CONDITIONS  OF 
THE  GLOBE. 

9.  Before  entering  upon  the  consideration  of  the  mate- 
rials which  compose  the  externaf  crust,  there  are  certain 
facts  concerning  the  general  structure  and  conditions  of  the 
globe  itself,  a  knowledge  of  which  is  necessary  to  the  prose- 
cution of  geological  research.     These  are  its  Figure,  Den- 
sity, Temperature,  and  Surface  Configuration  ;  the  distri- 
bution of  Land  and  Water,  Constitution  of  the  Sea,  the 
Atmosphere,  and  Planetary  Relations. 

FIGURE. 

10.  THE  FIGURE  OF  THE  EARTH  is  nearly  that  of  a  sphere 
or  globe.     A  diameter  (measure  through)  from  north  to 
south  is  said  to  be  polar ;  one  from  east  to  west,  equatorial. 
If  the  earth  were  perfectly  spherical,  these  diameters  should 
be  of  the  same  measure  ;  but  it  has  been  found  by  accurate 
investigation  that  the  polar  is  less  than  the  equatorial  by 
about  26J  miles.     According  to  Herschel — 

The  Equatorial  is        .         .         7925-648  miles. 
The  Polar  is  .  7899-170  miles. 


Difference,          .         .         .  26-478  miles. 

This  gives  a  flattening  or  compression  at  each  pole  of  about 
13^  miles ;  so  that  the  figure  of  the  earth  is,  strictly  speak- 
ing, that  of  an  oblate  spheroid. 

1 1 .  This  polar  compression  may  be  artificially  illustrated 
by  twirling  with  rapidity  a  ball  of  any  yielding  material,  such 
as  putty,  round  a  spit  thrust  through  it  for  an  axis,  when  a 

35.  What  preliminary  subjects  are  cited  for  inquiry  ? 

36.  Define  the  polar  and  equatorial  diameters  of  the  globe. 

37.  How,  and  why  do  they  differ,  and  to  what  extent  1 

38.  How  is  it  illustrated  and  explained  7 


DENSITY    OF    THE    EARTH.  19 

bulging  at  the  outer  surface  will  take  place,  causing  the  ball 
to  lose  its  original  globular  shape.  This  bulging  takes  place 
through  what  is  called  centrifugal  (flying  from  the  centre) 
force,  and  creates  a  difference  between  the  two  diameters 
of  the  ball  similar  to  that  which  exists  in  the  terrestrial  globe. 

12.  From  this  spheroidal  Jigure,  and  what  we  know  of 
the  law  of  centrifugal  force  acting  upon  a  body  of  yielding 
material,  it  is  concluded  that  the  earth  was  in  a  soft  or 
yielding  state  at  the  time  when  it  assumed  its  present  form. 
This  is  obviously  a  point  of  considerable  importance  in  the 
physical  history  of  our  planet,  and  therefore  demands  the 
especial  attention  of  the  geologist. 

DENSITY. 

13.  THE  DENSITY  OF  THE  EARTH  has  also  been  computed 
with  considerable  accuracy.     By  weighing  the  most  preva- 
lent rocks,  it  has  been  found  that  the  solid  crust  composed 
of  them  is  about  two  and  a-half  times  heavier  than  water; 
but  from  experiments  made  on  the  attraction  of  mountains 
of  known  bulk,  compared  with  the  attraction  and  bulk  of 
the  globe,  it  has  been  inferred  that  the  density  of  the  whole 
mass  is  five  times  that  of  water.     In  other  words,  the  earth, 
as  at  present  constituted,  is  Jive  times  heavier  than  a  globe 
of  water  of  similar  dimensions,  and  twice  that  of  the  rocks 
at  its  surface. 

14.  The  interior  or  central  material  of  the  earth  being 
thus  necessarily  heavier  than  the  rocks  which  form  its  crust, 
numerous  speculations  have  been  indulged  in  as  to  what 
the  nature  of  thase  materials  may  be.    It  has  been  said  that 
air,  water,  or  stone,  as  known  at  the  surface,  cannot  com- 
pose the  interior  parts;  for  if  the  law  of  gravitation  exert 
itself  uniformly  towards  the  centre,  either  of  these  would  be 
so  compressed  as  to  give  the  earth's  mass  a  mean  density 


39.  What  then  is  the  true  figure  of  the  earth  ? 

40.  What  inference  is  thence  drawn  t 

41.  What  of  the  density  of  the  earth,  and  how  computed  T 

42.  Wh«*  of  the  interior  of  the  earth  T 

43.  Whj  '.B  it  denied  that  it  is  either  air,  water,  or  stone  t 


20  GEOLOGY. 

greater  than  the  Jaws  of  attraction  will  allow.  Water,  for 
instance,  would,  at  the  depth  of  362  miles,  be  as  heavy  as 
quicksilver,  and  air  as  heavy  as  water  at  34  miles;  while  at 
the  centre,  the  density  of  marble  would  be  increased  119 
times!  To  make  their  suppositions  accord  with  the  mean 
density  of  the  earth,  that  is,  to  reconcile  the  forces  of  gravi- 
tation and  attraction,  theorists  have  successively  proposed 
gaseous  fluids,  heated  matter,  arid  even  light  itself,  as  the 
central  material. 

15.  Laying  aside  all  hypotheses,  our  knowledge  respect- 
ing the  density  arid  internal  structure  of  the  earth  may  be 
thus  summarily  stated: — 1.  The  density  of  the  rocky  crust 
is,  on  an  average,  two  and  a-half  times  that  of  water ;  2.  The 
mean  density  of  the  whole  mass  is  five  times  that  of  water; 
3.  The  central  parts  cannot  be  composed  of  similar  material 
with  the  crust,  otherwise  their  compression  would  become 
so  great  towards  the  centre,  that  the  mean  density  of  the 
earth  would  be  much  greater  than  it  is ;  and  4.  That  the 
condensation  of  the  central  masses  must  be  counteracted 
by  some  expansive  influence,  such  as  heat,  or  have  a  con- 
stitution unlike  any  substance  with  which  we  are  acquainted 
at  the  surface. 

TEMPERATURE. 

16.  THE    TEMPERATURE    OF    THE    EARTH  is  3    Subject  the 

consideration  of  which  exercises  a  most  important  influence 
on  the  reasonings  of  geologists.  There  is,  first,  the  surface 
temperature,  which  affects  the  growth  and  distribution  of 
plants  and  animals;  second,  the  temperature  of  the  crust, 
which  may  give  rise  to  gaseous  exhalations,  thermal  springs, 
mineral  and  metallic  transformations  ;  and,  third,  there  ap- 
pears to  be  an.  internal  or  central  temperature,  having  its 
seat  beneath  the  solid  crust,  and  which  seems  to  be  the 


44.  What  hypotheses  have  been  started  on  this  subject  T 

45.  How  far  may  it  be  said  that  our  knowledge  extends  on  this  subject  ? 

46.  What  agency  is  supposed  to  oppose   gravitation  and  attraction  in 

the  masses  of  the  earth's  centre  ? 

47.  What  three  divisions  are  made  in  the  temperature  of  the  earth? 

48.  What  is  ascribed  to  each  ? 


TEMPERATURE    OP    THE    EARTH.  21 

cause  of  volcanoes,  earthquakes,  and  other  similar   phe- 
nomena. 

17.  Of  the  surface  temperature^  we  know  that  it  is  influ- 
enced, first,  from  day  to  day,  and  from  season  to  season, 
by  the  heat  of  the  sun ;  second,  by  the  degree  of  latitude, 
being  warmest  at  the  equator,  and  gradually  diminishing 
towards   either   pole;    third,  by   the  distribution   of  land 
and  water,  the  sea  being  less  liable  to  sudden  fluctuations 
of  temperature  than  the  land;  fourtfi,  by  the  nature  of  the 
surface,  the  kind  and  colour  of  matter  variously  absorbing 
and  retaining  the  heat  derived  from  the  sun ;  and  lastly,  by 
the  elevation  of  the  land  above  the  mean  level  of  the  sea, 
the  more  elevated  being  the  colder  regions.     All  these  in- 
fluences are  at  present  in  active  force,  affecting  more  or  less 
the  growth  and  distribution  of  animal  and  vegetable  life; 
and  iu  like  manner  must  they  have  exerted  themselves  at 
former  periods,  though  perhaps  increased  or  counteracted 
by  certain  conditions  not  now  existing. 

18.  The  temperature  of  the  crust  may  be  affected  either 
by  heat  from  the  sun,  by  heat  created  by  chemical  action 
among  its  materials,  or  by  heat  from  the  interior.     During 
summer,  the  surface  is  heated  by  the  sun,  and  this  heat  is 
communicated  to  a  certain  depth;  during  winter  it  is  again 
given  off  to  the  surrounding  atmosphere  more  or  less,  ac- 
cording to  the  severity  of  the  winter.     This  alternate  re- 
ceiving and  parting  with  heat  may  differ  considerably  in  any 
particular  summer  or  winter,  but  over  a  number  of  years  it 
is  found  to  be  nearly  stationary;  that  is,  the  amount  of  heat 
received  arid  given  off  may  be  said  to  balance  each  other. 
According  to  this  doctrine,  the  earth  in  summer  will  be 
warmer  near  the  surface  than  it  is  at  small  depths;  and  in 
winter  will  be  colder  at  the  surface  than  at  depths  beyond 
the  influence  of  the  passing  cold. 

19.  The  heat  of  the  sun  can  only  affect  the  earth  to  a 
Umittd  d+pth;  for,  as  the  heat  of  summer  proceeds  down- 


49  What  influences  modify  the  surface  temperature  T 

50.  To  what  is  the  temperature  of  the  crust  ascribed  f 

51.  How  does  it  vary  1 

52    Explain  thin  phenomena. 

2 


GEOLOGY. 


wards,  it  is  arrested  by  the  cold  of  winter,  and  thus  con- 
tinually kept  within  a  given  limit.  By  actual  experiment, 
it  has  been  ascertained  that,  at  a  given  depth  beneath  the 
surface  of  the  earth,  there  is  a  point  at  which  the  tempera- 
ture remains  constantly  the  same,  being  uninfluenced  by 
any  causes  which  affect  the  surface.  This  depth  will  vary 
according  to  the  kind  of  material  of  which  the  crust  at  any 
given  place  is  composed,  be  these  materials  rocks,  sand,  or 
water;  but  in  no  instance  has  it  been  found  to  be  less  than 
60,  or  more  than  100  feet.  A  series  of  these  depths,  as 
represented  by  the  white  line  in  the  subjoined  diagram,  is 
called  by  geologists  the  stratum  of  invariable  temperature. 


Section,  showing  the  stratum  of  invariable  temperature,  and  relative 
thickness  of  the  solid  crust. 

20.  Proceeding-  beyond  this  invariable  stratum,  towards 
the  centre  (c),  it  has  been  found  that  the  temperature  gra- 
dually increases;  a  circumstance  which  attracted  the  atten- 
tion of  philosophers  more  than  a  century  ago.  In  1802 
D'Aubuisson  revived  the  investigation,  and  since  that  time, 
observations  have  been  made  in  the  principal  mines  of 
Europe  and  America.  The  greatest  depths  at  which  expe- 


53.  Does  the  material  of  which  the  crust  is  composed  affect  its  tempe- 

rature ? 

54.  To  what  depth  does  the  stratum  of  invariable  temperature  extend  ? 
65.  Does  the  temperature  increase  at  greater  depths  ? 


TEMPERATURE    OF    THE    EARTH.  23 

riments  have  been  conducted,  are  1713  feet  in  Mexico,  1584 
in  England,  and  about  1300  in  Germany;  and  in  all  of 
these  the  temperature  has  been  found  to  increase  according 
to  the  depth.  In  1827  M.  Cordier  published  a  memoir  on 
this  interesting  subject,  in  which  he  collected  the  observa- 
tions of  others  together  with  his  own ;  and  having  made 
allowance  for  the  heat  arising  from  the  breathing  of  miners, 
for  the  combustion  of  lamps,  and  communication  with  the 
atmosphere,  he  drew  the  following  general  conclusions: — 

1.  Below   the  invariable  stratum,  the  temperature  at  any 
given  depth  remains  perfectly  constant  for  several  years; 

2.  That  below  the  invariable  stratum  the  temperature  goes 
on  increasing  with  the  depth;  and,  3.  That,   taking  the 
average  of  observations,  this  increase  of  temperature  goes 
on  at  the  rate  of  one  degree  of  Fahrenheit's  thermometer 
for  every  45  feet.     Others  haye  allowed  60  feet  for  the  rise 
of  one  degree;  but  even  taking  this  lower  estimate,  it  must 
follow,  if  the  increase  go  on  in  the  sarrte  ratio,  that  a  tem- 
perature equal  to  100  degrees  of  Wedgewood's  pyrometer 
would  be   found  at  the  depth  of  160  miles.     But,  100  de- 
grees of  VVedgewood  is  sufficient  to  keep  in  fusion  any  of 
the  known   rocks,  so  that,  according  to  this  estimate,  the 
solid  crust  of  the  earth  cannot  be  more  than  61)  or  80  miles 
in  thickness — a  mere  fractional  film  of  the  distance  from 
the  surface  to  the  centre. 

21.  Of  the  internal  or  central  heat  of  the  globe,  we  know 
nothing  by  actual  experiment ;  but  are  left  to  infer  as  to  its 
amount  from  the  descending  increase  of  temperature  ob- 
servable in  the  solid  crust,  and  from  the  occurrence  of  hot- 
springs,  vapour  fissures,  and  volcanoes.  That  the  heat  of 
the  crust  increases  as  we  descend,  has  been  fully  established 
by  experiments  in  mines,  in  Artesian  wells,  and  in  the 
waters  of  other  deep-seated  springs;  and  if  this  tempera- 


56.  What  of  the  experiments  ? 

57.  Does  not  this  prove  that  very  great  heat  would  be  found  in  the  deep 

interior  of  the  globe  ? 

58.  In  what  ratio  does  the  temperature  increase  ? 

59.  At  this  rate,  what  would  be  the  heat  160  miles  below  the  surface  T 

60.  What  inference  is  authorized  from  this  fact  ? 

(j  1 .  What  other  facts  go  to  prove  the  central  heat  of  the  globe  to  be 
great  ? 


54  GEOLOGY. 

ture  goes  on  increasing  at  the  ratio  above-mentioned,  then 
the  interior  parts  must  be  heated  to  an  enormous  degree ; 
so  much  so,  indeed,  as  fully  to  counteract  that  law  of  com- 
pression formerly  adverted  to,  and  which  would  render  all 
known  matter,  if  placed  at  the  centre,  so  dense  as  to  be 
inconsistent  with  the  mean  density  of  the  globe. 

22.  Taking  all  circumstances  into  account,  the  following 
conclusions  seem  warrantable: — first,  that  the  interior  parts 
of  the  earth  are  heated  to  intensity;  second,  that  this  heat 
is  the  apparent  cause  of  volcanoes,  hot-springs,  and  other 
thermal  phenomena;  third,  that  the  solid  crust  derives  part 
of  its  heat  from  this  source;  fourth,  that  this  solid  crust  has 
partly  been  formed  by  the  cooling  of  an  original  igneous 
mass;  fifth,  that  if  volcanoes,  hot-springs,  &c.  take  place  at 
the  expense  of  this  internal  heat,  the  globe  must  be  gradu- 
ally cooling;  but, lastly,  that  from  the  bad  conducting  nature 
of  the  rocky  crust,  this  gradual  refrigeration  is  not  percep- 
tible within  any  given  time. 

EXPLANATORY  NOTE. 

DENSITY  (Lat.  densus,  thick) — thickness  or  compactness.  Density  is 
a  comparative  term;  gold,  for  instance,  being  denser  than  iron,  iron 
than  granite,  granite  than  sandstone,  sandstone  than  water,  and  water 
than  gas  ;  that  is,  a  cubic  inch  of  any  one  of  these  bodies  would  differ 
in  weight  from  a  cubic  inch  of  any  of  the  others.  To  render  this  idea 
of  density  more  definite,  water  at  the  temperature  of  60  degrees  has 
been  taken  as  the  standard  or  measure ;  hence,  if  water  be  assumed  as 
weighing  1,  the  rdcky  materials  composing  the  earth's  crust  will  be  2£, 
or  two  and  a-half  times  heavier  than  water. 

ARTESIAN  WELLS  (Artois,  a  district  in  France) — a  term  applied  to 
wells  sunk  by  digging  or  boring  perpendicularly  through  various  strata, 
from  the  circumstance  that  this  mode  was  first  practised  in  the  district 
above  referred  to. 

THERMAL  (Greek,  therme,  heat) — warm  or  hot.  Thermal  and  igne- 
ous nre  sometimes  used  indiscriminately;  but  it  is  more  accurate  to 
make  a  distinction.  Thus,  in  treating  of  volcanoes,  we  speak  of  igne- 
ous agency;  in  treating  of  hot-springs,  thermal  is  the  more  appropriate 
term. 

TEMPERATURE  OF  THE  EARTH. — The  chief  of  those  who  have  con- 


62.  What  conclusions  are  thus  reached  7 

63.  Define  density,  and  give  illustrations. 

64.  What  of  Artesian  wells  7 

65.  Define  thermal  and  igneous. 

66.  What  classes  of  experiments  have  been  made,  and  by  whom  7 


SURFACE    CONFIGURATION.  25 

ducted  experiments  relative  to  this  subject  are  Gemanne,  Saussure, 
D'Aubuisson,  Fourier,  Cordier,  Quetelet,  and  Arago,  in  France,  Ger- 
many, &c. ;  Sir  John  Leslie,  Fox,  Forbes,  &c.  in  Britain  ;  and  Hum- 
boldt,  in  Mexico.  Their  experiments  present  a  wonderful  degree  of 
coincidence,  and  are  chiefly  of  three  classes  : — 1.  Those  made  in  mine- 
ral veins,  01  in  mountain  masses,  such  as  granite ;  2.  Those  made  in 
stratified  rocks,  as  in  coal  mines ;  and,  3.  Those  made  in  Artesian 
wells  and  other  deep-seated  springs. 

SURFACE   CONFIGURATION. 

23.  THE  SURFACE  CONFIGURATION  OF  THE  EARTH  is  more 
the  study  of  physical  geography  than  of  geology  proper ; 
but  it  is  necessary  to  observe  in  what  manner  it  influences 
the  geological  changes  now  in  progress.  The  surface  of 
the  earth  is  extremely  irregular,  being  diversified  by  hills 
and  valleys,  rivers,  lakes,  seas,  &c.  Portions  of  it  are 
covered  with  woods  and  forests;  other  portions  are  elevated 
above  the  limits  of  vegetable  or  animal  life,  and  covered 
with  eternal  snows.  Some  parts  of  the  exposed  surfa'ce 
are  so  hard,  that  no  sensible  decay  is  experienced  for  ages; 
others  so  soft  and  loose,  that  scarcely  a  shower  falls  with- 
out carrying  away  a  portion  to  some  lower  level.  These 
differences  of  surface  material  are  also  influenced  by  steep- 
ness and  irregularity  of  position ;  the-  transporting  power 
of  streams  and  rivers  being  proportioned  to  the  rapidity  of 
their  descent.  These  are  familiar  instances  of  the  numerous 
changes  effected  by  diversity  of  surface  configuration ;  but 
the  student  has  only  to  cast  his  eye  over  his  own  district, 
to  be  convinced  haw  many  geological  results  depend  upon 
.^this  cause.  Those  immense  plains — the  steppes  of  North- 
•  ern  Asia,  the  prairies  of  North  arid  the  pampas  of  South 
America — must  affect  and  be  affected  in  a  different  manner 
from  the  Himmaleh,  Alps,  Andes,  and  other  mountain 
ranges.  The  showers  and  snows  which  produce  torrents 
and  avalanches  on  the  Alps,  form  merely  springs  and  harm- 
less streams  on  the  Apennines;  .and  while  the  sluggish 
river  is  forming  inland  plains  with  its  mud,  the  rapid  tor- 

67.  Name  the  varieties  of  surface. 

68-  How  do  these  modify  the  configuration  of  the  globe  1 

69.  What  illustrations  are  here  cited  1 


20  GEOLOGY. 

rent  is  carrying  its  burden  forward  to  the  bottom  of  the 
ocean. 

24.  The  surface  outline  of  the  earth  is  so  irregular  that 
even  physical  geography,  with  all  the  facilities  afforded  by 
modern  intercourse,  has  yet  presented  us  with  a  very  gene- 
ral description  ;  and  before  we  can  estimate  the  full  force 
of  this  configuration  as  a  geological  agent,  we  must  know 
more  of  the  relative  elevations  and  depressions  of  the  land, 
and  the  nature  of  the  rocky  substances  so  elevated  and 
depressed.     Of  the  surface  configuration  of  the  world  in 
its  earlier  ages,  we  have  no  positive  knowledge;  but  we  are 
certain  that  whatever  it  might  be,  it  would  materially  influ- 
ence the  changes  then  going  forward,  just   as  the  same 
cause  is  operating  at  the  present  moment. 

DISTRIBUTION    OP    LAND    AND    WATER. 

25.  THE  DISTRIBUTION  OF  LAND  AND  WATER,  upon  which 
so  many  geological  phenomena  depend,  is  influenced  by 
this  principle  alone :  namely,  that  so  long  as  the  same  quan- 
tity of  water  remains  on  the  globe,  a  fixed  amount  of  space 
will  be  required  to  contain  it.     If  the  difference  between  the 
elevations  and  depressions  of  the  solid  crust  be  small — in 
other  words,  if  the  hollows  in  which    lakes  and  seas  are 
spread  out  be  shallow — their  waters   must  extend  over  a 
greater  space :  and  if  these  hollows  be  deep,  the  waters  will 
occupy  less  extensive  areas.     The  operation  of  this  principle 
the  student  should  bear  in  mind;  for  if,  in  the  earlier  ages 
of  the  world,  the  elevation  of  the  land  was  less  general,  the 
waters  would  occupy  larger  spaces,  and  this  more  extended 
area  of  shallow  water  would  act  in  various  ways.     It  would 
render  the  climate  more  genial  and  uniform,  and  extending  a 
greater  surface  to  the  evaporating  power  of  the  sun,  rains 
and  atmospheric  moisture  would  be  more  prevalent.    These, 


70.  What  obscurity  still  rests  on  this  subject  ? 

71.  How  is  the  distribution  of  land  and  water  regulated  ? 

72.  How  illustrated  ? 

73.  What  hypothesis  is  suggested  ? 

74.  What  effect  would  result  upon  the  climate  ? 

75.  How  would  it  affect  animal  and  vegetable  life  1 


DISTRIBUTION    OF    LAND    AND    WATER. 


27 


28  GFOLOOY. 

again,  would  operate  on  the  amount  and  kind  of  animal 
and  vegetable  life  on  dry  land ;  while  the  shallow  waters 
themselves  would  be  more  productive  of  life,  it  being  a  well- 
known  fact,  that  shell-fishes  and  aquatic  plants  flourish  only 
at  limited  depths  around  the  shores.  Of  the  distribution 
of  land  and  water  at  any  former  period  of  the  world,  we  can 
only  infer  from  the  appearances  which  the  surface  and  rocky 
strata  present;  but  of  the  present  distribution,  we  have 
pretty  accurate  information,  with  the  exception  of  those 
regions  surrounding  either  pole. 

26.  TJie  proportion   of  dry  land  to  water,  as  at  present 
existing,  is  about  one  to  three  ;  that  is,  three-fourths  of  the 
whole  surface  of  the  globe  may  be  assigned  to  water.    The 
dry  land  presents  itself  in  islands  and  continents  variously 
situated;  but  the  student  has  only  to  cast  his  eye  over  a  map 
of  the  world,  to  observe  that   the  greater  portion  is  placed 
in  the   northern  hemisphere,  while  the  walers   occupy  the 
greater  portion  of  the  equatorial  and  southern  regions.   The 
relative  configuration  of  land  and  sea  is  extremely  irregular, 
and  no  conception  can   be   formed  of  it,  unless   from  the 
study  of  a  well-constructed  nmp. 

27.  This  configuration  exercises  a  most  important  influ- 
ence in  geological  operations  by  determining  the  direction 
of  oceanic  and  tidal  currents,  and  by  modifying  the  direc- 
tion and  force  of  waves.     Ocean-currents  carry  along  with 
them  plants,  trees,  and  other  floating  materials,  which  will 
be  arrested   wherever  the   land    presents  an   obstruction. 
Tides  exercise  a  powerful  transporting  influence  :  they  rise 
to  greater  or  less  heights,  according  as  they  are  obstructed 
by  the  outline  of  the  land;  and  while  they  sweep  headlands 
and  promontories  bare,  they  lay  down   sand  and  gravel  in 
sheltered  bays.     Waves  also  wear  away  the  land,  according 
as  the  line  of  coast  obstructs  or  favours  the  violence  of  their 


76.  What  data  have  we  of  the  ancient  state  of  things  ? 

77.  Where  is  our  knowledge  defective  of  the  present  ? 

78.  What  are  the  proportions  ? 

79.  How  is  the  land  distributed  chiefly  ? 

80.  Where  are  the  waters  most  abundant  ? 

81.  How  are  the  oceanic  and  tidal  currents  directeu  I 

82.  What  is  said  of  the  effect  of  these  ? 


CONSTITUTION    OF    THE    OCEAN.  29 

progress.  If,  therefore,  these  oceanic  agents  be  wearing 
away  dry  land  in  one  quarter,  and  filling  up  shallow  bays 
and  creeks  in  another;  if  springs  and  rivers  be  wearing 
down  inland  countries,  and  carrying  the  material  to  the  sea; 
and  if,  moreover,  earthquakes  and  volcanoes  be  here  sub- 
merging land,  and  there  elevating  the  bottom  of  the  ocean, 
the  relative  distribution  of  land  and  water  must  be  continu- 
ally fluctuating 

'28.  Of  the  depth  of  the  sea  little  is  known  from  actual 
soundings  ;  but  some  geologists,  taking  the  mean  elevation 
of  land  at  between  two  and  three  miles,  have  supposed  the 
mean  depth  of  ocean  not  to  exceed  that  extent.  As  the 
land,  however,  rises  variously  from  a  few  feet  to  more  than 
five  miles,  others,  attributing  the  same  irregularities  to  the 
bottom  of  the  ocean  as  are  seen  on  the  surface  of  the  land, 
have  assigned  various  depths,  from  a  few  feet  to  five  or  six 
miles.  From  calculations  which  have  been  recently  made 
on  the  velocity  of  tidal  waves,  which  are  found  to  proceed 
according  to  the  depth  of  the  channel,  it  is  estimated  that 
the  extreme  depths  of  the  Atlantic  are  about  50,000  feet, 
or  more  than  nine  miles. 

29.  Besides  the  Pacific,  Atlantic,  and  other  regions  of 
the  great  ocean,  there  are  large  inland  seas,  such  as  the 
Baltic  and  Mediterranean,  as  also  extensive  lakes  of  fresh 
and  salt  water,  all  of  which  exercise  important  and  varied 
functions  in  modifying  the  surface  of  the  globe.  From  the 
existing  arrangement,  we  are  naturally  led  to  entertain  the 
opinion,  that  conditions  similar  in  kind,  though  differing 
in  degree,  have  at  all  times  been  imposed  upon  land  and 
water. 

CONSTITUTION    OP    THE    OCEAN. 

3D.  OP  THE  CONSTITUTION  OF  THE  OCEAN  chemical  re- 
search  affords  us  pretty  accurate  data.  Water,  whether  fresh 


83.  To  what  causes  is  to  be  ascribed  the  fluctuation  in  the  relative  dis- 

tribution of  land  and  water  1 

84.  How  is  the  depth  of  the  sea  calculated  t 

85.  What  of  its  extreme  depth  ? 

b6.   What  bodies  of  water  are  named,  other  than  the  great  oceans  T 
2* 


30  GEOLOGY. 

or  salt,  may  contain  impurities — such  as  clay,  sand,  gravel, 
animal  and  vegetable  matter;  but  if  left  at  rest,  these  by 
their  own  weight  soon  fall  to  the  bottom.  Such  substances 
are  said  to  be  mechanically  suspended  ;  and  when  deposited 
at  the  bottom,  they  form  sediment.  Besides  impurities  of 
this  description,  water  may  contain  matter  which  will  not 
fall  down,  and  which  is  said  to  be  held  in  chemical  solution . 
Sea  water  of  the  Atlantic,  according  to  Dr.  Marcet,  contains 
4  3-lUth  grains  of  saline  matter  in  every  hundredth  ;  while, 
according  to  Dr.  Murray,  the  water  of  the  German  Ocean 
contains  only  3  3-100th  grains.  This  saline  matter  con- 
sists chiefly  of  muriate  of  soda  (common  salt),  sulphate  of 
s'oda,  muriate  of  lime,  and  muriate  of  magnesia.  It  has  been 
also  ascertained  that  the  southern  ocean  contains  more  salt 
than  the  northern;  that  small  inland  seas,  though  communi- 
cating with  the  ocean,  are  less  salt  than  the  ocean  ;  that  the 
Mediterranean  contains  a  greater  proportion  of  saline  matter 
than  the  Atlantic;  and  though  the  saltness  of  the  sea  be 
pretty  uniform  at  great  depths,  still,  at  the  surface,  owing 
to  the  admixture  of  rain,  river,  and  iceberg  water,  it  is  not 
quite  so  salt. 

31.  A  knowledge  of  the  constitution  of  the  ocean  is  ne- 
cessary to  the  explanation  of  numerous  facts  in  geology. 
The  saline  constituents   must  influence  more  or  less  all 
chemical  changes,  rock  deposits,  and  animal  and  vegetable 
life,  which  take  place  in  the  ocean.     From  these  constitu- 
ents shell-fish  and  coral  animals  derive  the  matter  of  which 
shell-beds  and  coral-reefs  are  constructed  ;  and  by  this  same 
constitution,  marine  animals  and  plants  are  made  to  assume 
a  character  which  distinguishes  them  from  the  inhabitants 
of  fresh  waters. 

32.  The  pressure  of  the  sea  (which  depends  on  its  depth) 
also  exerts  an  important  influence,  as  what  takes  place  near 

87.  What  impurities  are  found  in  water  T 

88.  How  are  they  suspended  ? 

89.  What  salts  are  found  in  sea  water  ? 

90.  How  are  they  held  in  combination  ? 

91.  What  variety  in  the  proportion  of  salts? 

92.  How  does  the  constitution  °r  the  ocean  influence  geological  phe- 

nomena ? 

93.  What  of  the  pressure  of  the  seat 


THE    ATMOSPHERE.  31 

the  surface  would  be  impossible  at  greater  depths.  There, 
animal  and  vegetable  life,  as  known  to  us,  cannot  exist; 
sand  and  mud,  which  remain  loose  near  the  shore,  would 
become  much  consolidated  if  subjected  to  this  pressure; 
and,  accoiding  to  the  experiments  ot'  Sir  James  Hall,  even 
limestone  could  be  fused  without  the  loss  of  its  carbonic 
acid.  Other  results,  depending  upon  the  present  constitution 
of  the  ocean,  might  be  pointed  out ;  but  enough,  we  trust, 
has  been  stated  to  impress  the  student  with  a  conviction  of 
its  geological  importance. 

THE    ATMOSPHERE. 

33.  THE  ATMOSPHERE,  which  everywhere  surrounds  the 
globe,  is  either  of  itself  the  immediate  cause  of  numerous 
terrestrial  changes,  or  it  is  the  medium  through  which  they 
are  effected.     The  air  is  a  gaseous  fluid,  produced  by  the 
combination  of  79   parts  of  nitrogen   with  21  of  oxygen,    _ 
every  100  such  parts  containing  a  small  portion  of  carbonic    ' 
acid  and  other  extraneous  impurities.     It  is  indispensable 
to  the  life  of  plants  and  animals,  and  an  alteration  of  its 
constitution  would  completely  change  the  relations  of  ani- 
mated nature ;  for,  while  a  greater  proportion  of  carbonic 
acid  would  be  highly  favourable  to  vegetation,  it  would  be 
utterly  destructive  to  animals.     The  proportion  of  nitrogen 
and  oxygen  in  the  atmosphere  is  at  present,  nearly  as  4  to  \q 
1 ;  change  this,  and  5  of  oxygen  with  1  of  nitrogen  forms  a  1    * 
compound  (nitric  acid,  or  aquafortis)  so  corrosive,  that  even  / 
the   metals  are  dissolved   by  it.     The  air  is  an  elastic  or 
compressible  medium;  and,  consequently,  the  lower  strata 
near  the  earth  will  be  compressed  by  the  weight  of  those 
above  them,  and  thus  the  air  will  become  rarer  as  we  as- 
cend.    From  measuring  the  rate  at  which  this  rarity  takes 
place,  it  has  been  calculated  that  at  the  height  of  forty-five 
miles  the  atmosphere  would  become  so  rare  as  to  be  inappre- 

94.  What  of  the  constitution  of  the  atmosphere? 

95.  How  would  a  change  in  its  composition  or  properties  affect  living 

beings  T 

96.  How  is  this  illustrated  T 

97.  What  of  atmospSeric  pressure  upon  the  rarity  of  the  air  ? 


32  GEOLOGY. 

ciable.     Forty  five  miles  has,  therefore  been  assumed  as  the 
limit  of  the  atmosphere. 

34.  This  aerial  medium  is  the  laboratory  in  which  nume- 
rous operations  are  effected.    Vapours,  rains,  snows,  clouds, 
winds,  and   electricity,  are  among  the  most  apparent  of 
these,  and  are  continually  influencing  the  earth's  surface; 
either  mechanically,  as  by  rains  and  winds ;  chemically,  as 
by  carbonic  acid;  electrically,  as  by  electrical  phenomena 
during  thunder  ;  or  vitally,  as  in  the  support  of  plants  and 
animals.     So  far  as  we  can  learn  from  human  history,  the 
constitution  of  the  atmosphere  has  continued  without  sen- 
sible  change ;    but  of  its  primeval  constitution  we   know 
nothing,  but  are  left  to  infer  of  its  conditions  from  the 
character  of  the  plants  and  animals  imbedded  in  the  rocky 
strata.     At  present,  atmospheric   agency  is  exerted  in  a 
thousand  ways,  and  analogy  warrants  us  to  conclude  that 
such  has  always  been  the  case;  this  agency  being  the  same 
in  kind,  though  perhaps  differing  in  degree. 

PLANETARY    RELATIONS. 

35.  THE  PLANETARY  RELATIONS  OP  THE  GLOBE  exert  a 
permanent,  and,  it  may  be,  sometimes  a  temporary  and  pe 
culiar  influence  on  the  changes  which  have  been  effected, 
or  are  now  going  forward,  on  its  surface.     From  the  sun 
it  derives  light  and  heat,  those  agencies  so  indispensable  to 
animal  and  vegetable  existence  ;  on  its  relation  to  the  sun 
and  moon  depend  those  important  tidal  influences  already 
adverted  to  ;  while  to  the  same  relation  it  owes  its  daily  and 
annual  revolutions,  with  all  their  attendant  results.     A  per- 
manent increase  or    diminution  of  the  sun's  heat  would 
change  the  whole  vegetable  and  animal  economy;  the  ap- 
proach of  a  comet  might  derange  the  present  order  of  the 

98.  What  atmospheric  phenomena  are  named  ? 

99.  In  how  many  ways  do  these  influence  the  earth's  surface  ? 

100.  What  of  the  permanence  of  the  atmospheric  constitution? 

101.  What  of  the  planetary  relations? 

102.  What  of  the  influence  of  the  sun  and  moon  ? 

103.  How  would  a  change  in  our  relation  to  the  sun  affect  us  ? 

104.  What  if  a  comet  should  approach  us  ? 


PLANETARY    RELATIONS    <>F    THE    GLOBE.  33 

globe's  rotations;  and  a  slight  shifting  of  the  earth's  axis,  \ 
so  as  to  displace  the  present  planetary  position  of  its  poles  •   ut 
and  equator,  would  so  alter  the  distribution  of  plants  and/ 
animals,  would  so   derange  its  surface  configuration,  and 
change  the  distribution  of  land  and  sea,  that  the  face  of 
nature  would  then  present  an  entirely  different  picture.    So 
far  as  history  or  the  calculations  of  astronomy  over  a  space 
of  3000  years  will  permit  us  to  infer,  no  such  revolutions 
have  taken  place;  nor  do  the  tides,  the  sun's  heat  or  light, 
seem  to  have  been  in  the  least  affected.     But  while  this  is 
true,  it  does  not  prevent  the  possibility  of  such  changes ; 
and  certain  geological  appearances  present  themselves  in 
the  earth's  crust,  which  cannot  be  accounted -fur  unless  by 
the  supposition  of  such  revolutions. 

36.  The  daily  and  annual  rotations  of  the  earthy  the 
sun's  light  and  heat,  the  ebb  and  flow  of  the  tides,  &c.  are 
permanent  occurrences,  dependent  on  the  planetary  relations 
of  the  globe;  catastrophes,  such  as  would  arise  from  the 
contact  of  a  comet,  a  change  in  the  position  of  the  earth's 
axis,  or  the  like,  would  be  temporary  and  peculiar. 

EXPLANATORY    NOTE. 

ELEVATIONS  AND  DEPRESSIONS. — These  are  terms  applied  to  the 
risings  and  fallings  of  the  surface  of  the  earth — from  the  slightest  un- 
dulation to  the  highest  mountain,  and  from  the  gentlest  hollow  to  the 
greatest  depth  of  ocean.  The  greatest  heights  with  which  we  are 
acquainted  are  those  of  the  Himmaleh  range  in  Asia,  the  Dhawalagiri 
Peak  being  28,077  feet,  and  the  Jewahir  25,747.  The  Andes,  in  South 
America,  are  the  next  in  order,  the  Nevado  di  Sorato  being  25,250  feet, 
and  Illimani  24,450.  In  Europe,  the  Alps  rise  (in  Mont  Blanc)  to 
lo,668  feet,  the  Pyrenees  to  1 1 ,283  ;  and  in  Africa,  Geesh,  in  Abyssinia, 
is  15,000,  and  the  Peak  of  Teyde  (Tenerifle)  gives  12,180.  As  some 
parts  of  the  dry  land  are  above  the  level  of  the  sea,  so  also  some  por- 
tions are  beneath — such  as  the  central  regions  of  Asia  around  the  Cas- 
pian and  the  Aral  seas,  where  the  surface  has  been  ascertained  to  be 
from  80  to  100  feet  actually  lower  than  the  level  of  the  ocean.  But  the 
greatest  depressions  in  the  solid  crust,  are  those  occupied  by  the  sea, 
where  actual  soundings  have  reached  depths  of  nearly  a  thousand 

105.  Suppose  the  axis  of  the  earth  slightly  shifted  T 

106.  Is  there  any  proof  of  any  of  these  changes  within  3000  years  T 

107.  What  are  permanent  occurrences  ? 

108.  What  of  the  elevations  and  depressions  of  the  surface  of  the  globe  f 

109.  Name  the  examples  here  ci'.ed. 


34  GEOLOGY. 

fathoms ;  and  to  which  other  calculations  have  assigned  a  depth  of  no 
less  than  nine  miles. 

AVALANCHES  (French,  lavanches,  avalanges) — are  accumulations  of 
enow,  or  of  snow  and  ice,  which  descend  from  lofty  mountains,  like  the 
Alps,  into  the  valleys  beneath.  They  originate  in  the  higher  regions 
of  mountains,  and  begin  to  descend  when  the  gravity  of  the  mass  be- 
comes too  great  for  the  slope  on  which  it  rests,  or  when  fresh  weather 
destroys  its  adherence  to  the  surface.  Avalanches  are  generally  dis- 
tinguished as  drift,  rolling,  sliding,  and  glacier  or  ice  avalanches. 
Drift  are  those  caused  by  the  action' of  the  wind  on  the  snow  while 
loose  and  powdery ;  rolling,  when  a  detached  piece  of  snow  begins  to 
roll  down  the  steep — it  licks  up  the  snow  over  which  it  passes,  and 
thus  acquires  bulk  and  force  as  it  descends  ;  sliding  when  the  mass 
looses  its  adherence  to  the  surface,  and  descends,  carrying  every  thing 
before  it  which  is  unable  to  resist  its  pressure ;  and  glacier  or  ice,  when 
pieces  of  frozen  snow  and  ice  are  loosened  by  the  heat  of  summer,  and 
precipitated  into  the  plains  below. 

ICEBERG  (German  eis,  ice,  and  berg,  mountain) — the  name  given  to 
the  masses  of  ice  resembling  mountains,  often  found  floating  in  the 
polar  seas.  They  are  sometimes  formed  in  the  sea  itself  by  the  accu- 
mulation of  ice  and  snow  ;  at  other  times  they  seem  to  be  glaciers 
which  have  been  piling  up  on  a  precipitous  shore,  till  broken  off  and 
launched  into  the  ocean  by  their  own  weight.  Masses  of  this  kind  have 
been  found  in  Baffin's  Bay  two  miles  long  and  half  a  mile  in  breadth, 
rising  from  40  to  200  feet  above  the  water,  and  loaded  with  beds  of 
earth,  gravel,  and  rocks.  Some  idea  of  the  size  of  these  icebergs  may 
be  formed  from  the  fact,  that  the  mass  of  ice  below  the  level  of  the 
water  is  about  eight  times  greater  than  that  above.  As  they  float  to- 
wards warmer  regions,  they  gradually  dissolve,  dropping  their  burden 
of  rock  debris,  and  thus  strewing  the  bottom  of  the  ocean  with  clay, 
gravel,  and  boulder  stones,  some  of  which  are  many  tons  in  weight. 

PROPORTION  OF  LAND  AND  SEA. — The  proportion  of  land  to  sea  is, 
accurately,  as  266  to  734.  If,  therefore,  the  whole  superficies  of  the 
globe  be  taken  at  196,816,658  square  miles,  it  follows  that  the  dryland 
occupies  52, 353,231  square  miles,  and  the  ocean  an  area  of  144,463,427 
square  miles. 

PRESSURE  OF  THE  ATMOSPHERE. — If  the  density  of  air  at  the  surface 
of  the  earth  be  represented  by  one,  at  seven  miles  above  the  earth  it 
will  be  l-4th,  at  fourteen  miles  l-l6th,  at  twenty-one  miles  it  will  be 
l-64th,  and  so  on.  This  property  of  air  would  lead  to  the  idea  of  an 
indefinite  extension  of  the  atmosphere,  but  there  is  evidently  an  ap- 
preciable limit  to  this  ;  and  hence,  by  calculations  relative  to  the  pro- 
gress of  the  sun's  light,  and  other  astronomical  phenomena,  forty-five 
miles  has  been  fixed  as  the  altitude  of  the  atmosphere.  Air  is  pon- 
derable— 100  cubic  inches  at  the  temperature  of  60  degrees  weighing 

110.  Define  avalanches,  and  explain  their  variety. 

111.  What  are  icebergs,  and  how  formed  ? 

112.  What  of  their  size  and  depth  ? 

113.  How  is  the  proportion  of  land  to  sea  stated  in  figures  1 

114.  How  is  it  that  forty-five  miles  have  been  fixed  upon  as  the  altitude 

of  our  atmosphere  ? 

115.  Is  air  ponderable,  and  what  is  its  weight  T 


CAUSES  MODIFYING  THE  STRUCTURE  OF  THE  GLOBE.     35 

30£  grains.  A  perpendicular  column  of  the  whole  atmosphere  is  balanced  ; 
by  one  of  mercury  rising  to  30  inches  ;  hence  the  atmosphere  presses  on  ' 
every  ciibic  inch  of  surface  with  a  weight  equal  to  16  pounds. 

PRESSURE  OF  THE   OCEAN — Water  being  slightly  compressible,   it 
follows,  as  in  the  atmosphere,  that  water  at  great  depths  in  the  ocean 
will   be   denser   than  at  the    surface.     According   to   calculations  by  . 
Oersted,  water  at  the  depth  of  100  feet  is  compressed  l-340th  part  of  i 
its  own  bulk. 

CAUSES  MODIFYING  THE  STRUCTURE  AND 
CONDITIONS  OF  THE  GLOBE. 

37.  Had  the  general  structure  and  conditions  of  the  globe, 
as  described  in  the  foregoing  section,  been  subjected  to  no 
modifying  causes,  they  would  have  remained  unchanged 
from  the  beginning  of  time,  and  the  earth  would  have  pre- 
sented now  the  same  appearance  as  at  any  former  period. 
But  these  very  conditions  are   themselves  the  causes  of 
change,  for  they  mutually  act  upon  each  other,  and  give 
rise  to  innumerable  agents,  which  have  continued  through 
all  time  to  modify  the  face  of  nature.     Thus,  for  example, 
the  planetary  relations  of  the  earth  enable  it  to  derive  heat 
from  the  sun  ;  this  heat  vaporizes  the  water  of  the  ocean,  the 
vapour  produces  rains,  these  rains  form  springs  and  rivers, 
the  rivers  wear  down  the  land,  and  thus  change  the  surface 
configuration  ;  the  matter  borne  down  by  the  rivers  forms 
new  land  along  the  sea-shore,  altering  the  distribution  of 
land  and  water;  and  this  distribution  of  land  and  water 
materially  affects  the  kind  and  distribution  of  plants  and 
animals.     This  is  a  simple  instance  of  the  changes  pro- 
duced by  the  action  and  reaction  which  takes  place  among 
the  general  conditions  of  the  globe ;  and  the  student  would 
do  well,  at  this  stage  of  his  progress,  to  familiarize  himself 
with  such  trains  of  cause  and  effect,  as  it  is  only  by  the 
ready  application  of  similar  reasoning  that  he  will  be  able 
to  comprehend  many  of  the  phenomena  hereafter  described. 

38.  The  modifying  causes  produced  by  the  mutual  influ- 

116.  What  is  the  pressure  of  the  atmosphere  upon  a  cubic  inch  ? 

117.  What  of  the  pressure  of  the  ocean  t 

118.  What  causes  modify  the  structure  and  conditions  of  the  globe  ? 

119.  Describe  the  effect  of  the  sun's  heat  on  the  ocean  t 

120.  What  of  rivers,  and  the  changes  they  produce  1 


36  GEOLOGY. 

ence  of  the  general  conditions  already  considered  are  ex- 
ceedingly numerous  and  varied.  At  present,  it  is  necessary 
to  notice  only  such  as  seern  to  account  for  the  principal 
facts  connected  with  the  solid  materials  which  form  the 
crust  of  the  globe,  and  the  order  and  manner  of  their  ar- 
rangement. These  causes,  or  agents,  may  be  divided  into 
four  great  classes;  namely,  ATMOSPHERIC,  AQUEOUS,  IG- 
NEOUS, and  ORGANIC  ;  and  their  modes  of  action  may  be 
either  mechanical,  chemical,  electrical,  or  vital. 

ATMOSPHERIC    AGENCIES. 

39.  ATMOSPHERIC  AGENTS  act  either  mechanically  or 
chemically :  the  action  of  wind  in  drifting  loose  sand  13 
mechanical,  the  action  of  the  air  in  weathering  the  surface 
of  rocks  is  chemical.  The  atmosphere  may  either  act  di- 
rectly, as  in  the  case  of  winds,  or  indirectly,  as  in  the  pro- 
duction of  waves,  the  effects  of  which  on  the  sea-coast  are 
often  destructive  and  extensive.  The  changes  produced 
on  the  earth's  crust  by  atmospheric  agency  are  sometimes 
slow  and  gradual,  such  as  in  the  crumbling  down  of  rocks; 
or  immediate,  as  in  the  uprooting  of  forests  by  tempests, 
and  the  covering  of  green  valleys  by  barren  sand-drift. 
The  air,  or  atmosphere,  is  one  of  the  most  important  ele- 
ments, and  is  more  or  less  connected  with  every  operation 
in  nature.  By  it  the  sun's  light  and  heat  are  equally  dif- 
fused ;  it  is  indispensable  to  the  existence  of  plants  and 
animals;  and  it  is  the  great  laboratory  in  which  the  waters 
of  the  ocean  are  purified  and  distributed  over  the  face  of 
the  globe.  These  may  be  said  to  be  universal  functions 
of  the  atmosphere.  It  also  acts  peculiarly,  and  over  limited 
extent,  as  in  the  production  of  winds,  frost,  heat,  electricity, 
and  gaseous  admixtures. 

121.  What  four  great  classes  of  agency  are  named  ? 

122.  What  of  their  modes  of  action  ? 

123.  How  do  atmospheric  agents  act  ? 

124.  Give  examples  of  each. 

125.  What  of  direct  and  indirect  action  ? 

126.  Name  instances  of  gradual  and  immediate  action. 

127.  What  of  the  universal  functions  of  the  atmosphere? 

128.  In  what  phenomena  does  it  act  peculiarly  ? 


ATMOSPHERIC    AGENCIES.  37 

40.  Winds  are  aerial  currents.     When  the  air  of  one 
region  becomes  heated  or  rarefied,  the  colder  and  heavier  air 
of  the  surrounding  regions  rushes  in  to  restore  the  balance, 
and  thus  atmospheric  currents  are  produced.     These  cur- 
rents are  extremely  unstable,  blowing  without  regard   to 
time  or  direction,  and  modified  and  obstructed  in  a  thousand 
ways  by  hills,  valleys,  and  other  surface  irregularities.  They 
are   equally  unstable  in  their  velocity,  varying  from  the 
gentlest  breeze  to  the  fiercest  hurricane  which  overturns 
cities  and   uproots  forests.     But  though  characterized  by 
these  irregularities  over  the  greater  portion  of  the  globe, 
there   are   regions  over  which   they  pass  with  wonderful 
steadiness  for  months    together.     The  trade-winds  which 
take  place  within  the  tropics  possess  this  character,  and 
blow  Irom  east  to  west  with  little  variation  of  direction  or 
force.   The  monsoons,  which  are  connected  with  the  trade- 
winds,  are  also  preity  regular;  and  in  most  countries  an 
east,  a  south,  or  a  west  wind,  is  found  to  prevail  over  other 
directions,  and*  that  at  particular  periods  of  the  year.     Of 
the  phenomena  of  winds  in  the  earlier  eras  of  the  world  we 
have  no  knowledge;    but  we  are  warranted  to  conclude, 
that  since  the  elevation  of  dry  land,  and  the  distribution  of 
land  and  water,  they  have  been  analogous  to  what  is  now 
in  daily  occurrence. 

41.  Wind  acts  on  all  loose  material,  bearing  it  from  ex- 
posed to  sheltered  places.     Sand,  gravel,  and  loose  shells 
are  most  frequently  shifted  by  its  force,  and  blown  into  hil- 
locks, or  scooped  out  into  hollows,  without  order  or  regu- 
larity.    All  those  extensive  tracts  of  sand  found  along  the 
sea-coast — known  in   Scotland  as  links,  and  as  downs  in 
England — owe  their  surface  formation  to  the  wind.     The 
sand  collected  in  bays  and  creeks  by  the  waves  and  tides 
of  the  ocean,  is  no  sooner  left  dry  by  the  tide,  and  exposed 
to  the  sun,  than  it  becomes  light,  and  easily  acted  upon  by 
the  wind,  which  raises  it  into  knolls  and  ridges  beyond  the 

129.  Define  winds,  when  and  how  produced  t 

130.  How  modified  and  varied  ? 

131.  What  of  trade-winds  T 

132.  What  are  monsoons  ? 

133.  Upon  what  materials  do  winds  act,  and  what  examples  ajc  cited  T 


38  GEOLOGY. 

influence  of  the  returning  tide.  By  and  by  a  scanty  herbage 
gathers  over  the  sand,  arid  thus,  in  course  of  ages,  extensive 
downs  are  formed.  In  a  similar  manner  the  wind  acts 
upon  the  sandy  deserts  of  Arabia  and  Egypt,  continually 
shifting  their  surface  ;  and  if  it  sets  in  from  any  prevailing 
direction,  these  sands  are  carried  forward,  year  after  year, 
burying  trees,  fields  and  villages,  and  thus  converting  fertile 
districts  into  barren  wastes.  When  a  river  enters  the  sea 
through  a  sandy  district,  it  has  a  tendency  frequently  to  shift 
its  channel ;  and  this  tendency  is  greatly  increased  by  winds 
damming  up  the  current  with  drifted  sand.  Volcanoes  oc- 
casionally discharge  showers  of  dust  and  ashes,  which, 
during  high  winds,  are  carried  over  many  leagues  of  surface, 
or  borne  out  to  the  ocean.  During  calm  weather  volcanic 
dust  and  ashes  would  fall  in  the  neighbourhood  of  the 
crater ;  during  high  winds  they  may  be  deposited  at  vast 
distances  from  their  original  sources.  Such  examples  as 
the  above  are  the  ordinary  actions  of  wind:  the  uprooting  of 
forests,  the  destruction  of  cities,  and  the  like,  are  extraordi- 
nary, and  are  caused  by  whirlwinds  and  hurricanes. 

42.  Frost  exercises  a  slow  but  permanent  influence  in  mo- 
difying the  surface  configuration  of  the  globe.     When  the 
heat  of  the  surrounding  atmosphere  falls  below  32  degrees 
of  the  thermometer,  water  begins  to  freeze,  and  in  this  state 
expands.     During  winter  or   moist  weather,  water  enters 
between  the  particles  of  all  rocky  matter  at  the  surface  of 
the  earth,  and  also  into  the  larger  fissures;  and   the  expan- 
sion of  this  water  by  frost  separates  these  particles,  and 
leaves  them  to  fall  asunder  when  the  ice  is  dissolved.    This 
takes  place  more  or  less  every  winter ;  and  there  is  not  a 
cliff  or  hill  side  but  bears  evidence  of  this  kind  of  action. 
The  effect  of  frost  in  crumbling  down  rocky  material  has 
been  long  observed;  the  farmer  takes  advantage  of  it  to 
pulverize  his  soil ;  and  in  some  districts  slate  and  flagstone 
are  split  into  thin  lamina?  by  being  exposed  to  the  frost. 

43.  Of  the  amount  of  change  produced  by  frost,  it  would 

134.  Name  the  changes  produced  by  the  winds  upon  sand. 

135.  What  instances  are  cited  of  ordinary  and  extraordinary  winds  ? 

136.  How  does  frost  modify  the  earth's  surface  ? 

137.  Give  the  examples  and  illustrations  in  the  text. 


ATMOSPHERIC    AGENCIES.  39 

be  difficult  to  form  an  estimate ;  but,  taking  it  over  a  lapse 
of  ages,  there  can  be  little  doubt  that  it  has  been  an  impor- 
tant agent.  In  mountain  regions,  such  «s  the  Alps,  its 
effects  are  strikingly  apparent  in  the  formation  of  ava- 
lanches; and  in  northern  latitudes  the  iceberg  is  one  of  its 
familiar  productions.  The  action  of  frost  in  crumbling 
down  a  rocky  surface  seems  slow  and  insignificant,  but 
when  we  look  upon  the  avalanche  carrying  rocks,  gravel, 
trees,  and  houses  before  it,  and  burying  them  in  one  com- 
mon ruin ;  when  we  look  upon  the  iceberg  laden  with  huge 
stones,  and  dropping  them  into  the  ocean  as  it  dissolves, 
we  are  more  impressed  with  its  importance,  and  are  ena- 
bled to  account  for  certain  geological  appearances  which  no 
other  agency  could  have  produced.  (See  note,  p.  34.) 

44.  Solar  heat  and  light  may,  without  much  impropriety, 
be  classed  as  atmospheric  agents,  as  the  atmosphere  is  the 
medium  through  which  they  act,  and  by  which  they  are 
modified.     Water  conducts  heat  faster  than  air,  and -air,  at 
the  surface  of  the  earth,  faster  than  highly  rarefied  air  at 
great  heights;  hence  different  conditions  of  the  atmosphere 
may  have  hitherto  conducted  more  heat  to  the  earth's  sur- 
face.    The  quantity  of  light  which  reaches  the  earth  de- 
pends upon  the  serenity  of  the  atmosphere,  and  the  height 
of  the  sun  above  the  horizon  ;  hence,  also,  a  different  con- 
dition of  atmosphere  would  produce  a  different  amount  of 
light. 

45.  Heat  and  light  are  indispensable  to  vegetable  and 
animal  existence ;  and  the  kind  and  number  of  plants  and 
animals  depend,  in  a  great  measure,  upon  the  degree  and 
uniformity  of  their  influence.     Heat  converts  water  into 
vapour,  and  vapour  forms  dews,  rains,  &c.     The  amount 
of  vapour,  and  consequently  the  amount  of  rain,  will  de- 
pend upon  the  degree  of  heat ;  and  hence  the  heavy  peri- 
odical rains  of  the  tropics.     A  higher  degree  of  heat  all 
over  the  earth  would  greatly  increase  the  amount  of  rains, 
these  rains  would  form  more  gigantic  rivers,  and  geological 
effects  of  corresponding  magnitude  would  follow. 

138.  How  is  the  power  of  frost  shown  ? 

139.  How  are  solar  heat  and  light  modified  by  the  atmosphere  7 

140.  What  effects  are  ascribed  to  heat  and  light  ? 


43  CEOLOGY. 

46.  Of  the  amount  of  solar  heat  received  by  the  earth  at 
any  former  period,  we  are  left  to  infer  from   the  kind  of 
plants  and  animals  which  are  found  imbedded  in  the  rocky 
strata  ;  a  scantiness  and  peculiar  character  of  these  remains 
indicating  a  temperature  analogous  to  that  of  the    polar 
regions,  and  numerical  amount  and  external  form  indicating 
a  climate  similar  to  that  of  the  tropics. 

47.  Electricity  is  only  ranked  among  atmospheric  agents, 
though  electric,  galvanic,  and  magnetic  influences  may  be 
going  on   in  the  crust  of  the  globe  totally  independent  of 
the  atmosphere.     The  effects  of  these  subtle  forces  are  not 
easily  calculated ;  and  what  connexion  they  may  have  with 
earthquakes,  with  the  formation  of  metallic  veins,  and  simi- 
lar phenomena,  geology  has  not  been  able  to  determine.  We 
know  that  the  hardest  and  most  untractable  substances  in 
nature  can  be  artificially  dissolved  and  reconstructed  by  the 
aid  of  electricity;  this  force  sometimes  acting  slowly  and 
insensibly,  and  other  times  with  rapidity  and  violence.    We 
know,  also,  that  what  the  chemist  has  not  been  able  to  effect 
by  the   most  powerful   charges  of  electricity,  has  been  ac- 
complished by  the  slow  and  almost  insensible  effects  of  the 
same  agent.     What  takes  place  in  the  laboratory  of  the  che- 
mist may  be  daily  occurring  in  nature.     We  occasionally 
perceive  the  violent  effects  of  electricity  during  a  thunder- 
storm ;  but  these  may  be  trifling  in  comparison  with  what 
is  hourly,  but  insensibly,  taking  place  among  the  materials 
which  compose  the  crust  of  the  earth.     We  often  hear  of 
the  disasters  of  a  tropical  thunder-storm,  where  the  electric 
fluid  demolishes  houses,  rends  trees,  sets  fire  to  forests,  or 
shivers  rocks ;  but  these  consequences,  though   startling, 
produce  no  extensive  terrestrial  changes ;  so  that  it  is  to 
the  slow  and  unseen  agency  of  this  power  in  producing 
peculiar  transformations  of  metallic  and  other  matter,  that 
its  importance  in   geological   reasoning   is   mainly  to   be 
ascribed. 

141.  What  indications  of  solar  heat  are  found  in  fossil  remains  1 

142.  Is  electricity  always  an  atmospheric  agent  ? 

143.  What  phenomena  may  depend  on  this  agent? 

144.  What  is  said  of  the  variable  actions  of  electricity  ? 

145.  Which  kind  of  electrical  agency  is  regarded  chiefly  in  geological 

inquiries  ? 


ATMOSPHERIC    AGENCIES.  4  I 

48.  The  gaseous  constitution  of  the  atmosphere  acts  che- 
mically, not  mechanically.     In  its  ordinary  state,  as  we 
have  already  seen,  every  100  parts  are  composed  of  79 
nitrogen  and  21  oxygen,  with  a  small  proportion  of  carbo- 
nic acid,  amounting  to  little  more  than  one  part  in  a  thou- 
sand.    This  constitution  is  essential  to  animal  and  vegeta- 
ble life;  hence  the  student  can  readily  conceive  how  any 
extensive  alteration  of  this  mixture  would  operate.     Car- 
bonic acid   gas  is  given  off  by  some  springs,  by  volcanic 
fissures,  and  by  similar  sources  both  in  the  sea  and  on  dry 
land.     This  gas  is  destructive  to  life;  and  consequently 
shoals  of  fishes,  or  herds  of  animals,  coming  in  contact 
with  any  extensive  exhalation  of  it,  would  be  instantly  suf- 
focated.    Other  gaseous  fumes  are  also  destructive  to  life ; 
and  bearing  these  facts  in  mind,  we  may  be  enabled  to  ac- 
count for  peculiar  accumulations  of  animal  remains  in  cer- 
tain situations  in  the  rocky  strata. 

49.  Rocks  exposed  to  the  atmosphere  absorb  air  and  mois- 
ture, and  the  action  of  this  air  and  moisture  weathers,  or 
dissolves  the  union  of  the  outer  particles.     These  outer 
particles  fall  off  by  the  force  of  gravity;  another  set  of  par- 
ticles are  exposed  to  the  same  wasting  influence;  and  thus, 
year  after  year,  every  rock  and  mountain  is  losing  more  or 
less  of  its  material. 

50.  Oxygen  and  carbonic  acid  are  the  principal  agents 
in  this  operation.     All  metallic  substances  are  acted  on  by 
oxygen ;  it  tarnishes  their  surface,  gradually  eats  into  their 
mass,  and  in  time  converts  them  into  a  loose  powdery  sub- 
stance.    Iron  affords  a   similar  illustration  of  this   fact : 
however  well  polished,  if  exposed  to  air  and  damp,  it  be- 
gins to   rust,  film  after  film,  till   the  whole  is  in  time  con- 
verted into  a  reddish  powder,  called  rust,  or  oxide  of  iron. 
All  the  igneous  rocks,  and  most  of  the  aqueous,  contain 
iron  disseminated  in  minute  particles  through  their   mass, 
and  are  therefore  liable  to  be  acted  upon  by  oxygen.     It  is 

146.  What  of  the  gases  of  the  atmosphere  T 

147.  Whence  may  carbonic  acid  be  given  off"  in  quantities  1 

148.  What  fossil  remains  may  be  thus  accounted  for  ? 

149.  What  of  weathering  rocks  T 

150.  What  action  is  ascribed  to  the  oxygen- of  tho  atmosphere  T 


42  GEOLOGY. 

this  oxide  of  iron  which  gives  the  reddish  colour  to  many 
rocks  and  mineral  waters. 

51.  The  formation  of  many  soils  is  owing  to  this  pulver- 
izing power  of  the  atmosphere;  and  as  their  loose  matter  is 
washed  down  by  rains  and   rivers,  a  new  supply  is  formed 
by  further  disintegration  of  the  rocks  beneath.     We  have 
no  means  of  ascertaining  the  amount  of  change  produced 
by  the  chemical   constitution  of  the  atmosphere ;  but  this 
we  know,  that  it  must  hav-e  exerted  itself  through  all  time 
most  powerfully  in  warm  damp  climates,  and  least  where 
the  air  was  clear  and  arid.     Soft  clays  and  shales  are  easily 
weathered  down;  so,  also,  are  all  kinds  of  volcanic  rocks; 
and  even  granite  has  been  known  to  be  pulverized  to  the 
depth  of  three  inches  in  six  years. 

52.  The  atmospheric  agents  chiejly  instrumental  in  modi- 
fying the  crust  of  the  globe,  all,  more  or  less  exert  a  de- 
grading or  wasting  influence;  that  is,  a  tendency  to  wear 
down  the  surface  to  a  lower  level.     Wind  occasionally  pre- 
sents an  exception  to  this  statement,  and  tends  to  raise  the 
surface;  as  in  the  formation  of  downs  and   sand-hills,  of 
considerable  elevation,  like  those  of  Barry  at  the  mouth  of  the 
Tay.  Atmospheric  forces  act  either  mechanically,  chemically, 
or  vitally;  are  universal  in  their  operations,  with  perhaps  the 
exception  of  frost  in  the  tropics;  and  must  have  exercised 
an  important  influence  on  the  geological  conditions  of  the 
earth  from  the  beginning  of  time. 

EXPLANATORY    NOTE. 

ATMOSPHERIC,  AQUEOUS,  IGNEOUS,  AND  ORGANIC. — The  student 
should  make  himself  perfectly  familiar  with  the  application  of  these 
terms.  Wind,  for  example,  is  a  purely  atmospheric  agent ;  springs, 
rivers,  and  waves,  are  aqueous  agents ;  volcanoes  are  igneous  agents, 
and,  geologically  speaking,  the  term  is  chiefly  applied  to  forces  or 

151.  What  is  said  of  the  rust  of  iron  ? 

152.  How  may  soils  be  thus  formed  ? 

153.  What  instances  are  cited  of  the  pulverizing  power  of  the  atmos- 

phere ? 

154.  To  what  kind  of  action  is  this  to  be  ascribed  ? 

155.  What  exception  to  the  wasting  effects  of  this  class  of  agents  ? 

156.  What  exception  is  admitted  to  their  universal  action  ? 

157.  Name  the  illustrations  in  the  Note. 


ATMOSPHERIC    AGENCIES.  43 

results  depending  upon  the  internal  heat  of  the  earth  ;  and  organic 
agents  ire  such  as  arise  from  animal  or  vegetable  life.  Organic  (Greek, 
organen,  an  instrument  or  machine)  is  applied  to  vegetable  or  animal 
structures,  as  being  made  up  of  parts  nicely  adapted  to  each  other.  All 
matter  resulting  from  the  growth  or  decay  of  plants  and  animals  is  said 
to  be  organic. 

MECHANICAL,  CHEMICAL,  ELECTRICAL,  AND  VITAL. — A  piece  of 
chalk  may  be  brayed  to  powder  by  pounding  it  in  a  mortar ;  it  may 
also  be  reduced  to  powder  by  dissolving  it  in  sulphuric  acid  ;  in  the 
former  instance  the  action  is  mechanical,  in  the  latter  chemical.  In 
whatever  manner  electricity  acts,  the  action  is  said  to  be  electrical ;  the 
reconversion  of  blue  vitriol  (sulphate. of  copper)  into  metallic  copper, 
as  is  done  in  electrotyping,  is  an  example  of  this  kind  of  action.  Vital 
is  applied  to  any  sort  of  action  depending  on  life,  whether  in  animals  or 
vegetables. 

WINDS. — Besides  the  trade-winds,  blowing  within  the  25th  degree 
of  latitude  on  either  side  the  equator,  there  are  the  monsoons,  which 
are  merely  the  trade- winds  diverted  north  or  south  by  the  land  that  --» 
lies  within  these  parallels ;  the  simoom,  a  burning  pestilential  blast,  4 
which  rushes  with  fury  over  the  sandy  deserts  of  Arabia ;  the  harmat- 
tan,  a  cold  dry  wind,  frequent  in  Africa  and  in  Eastern  countries ; 
the  sirocco,  a  hot,  moist,  and  relaxing  wind,  which  visits  Italy  from  the 
opposite  shores  of  the  Mediterranean ;  the  bize,  a  cold  frosty  wind, 
which  descends  from  snow-covered  mountains,  such  as  the  Alps  ;  and 
whirlwinds  and  tornados,  that  are  common  to  all  countries,  but  most 
destructive  in  warm  regions. 

FREEZING. — Water,  at  the  temperature  of  40  degrees,  may  be  said  • 
to  be  stationary  as  to  bulk ;  but  if  the  temperature  be  reduced,  it  be- 
gins to  expand,  till,  at  32  degrees,  it  freezes,  and  is  converted  into  solid 
ice,  in  which  state  it  is  1-1 4th  larger  than  its  original  volume.  On  the 
other  hand,  if  the  temperature  be  increased,  the  water  is  gradually  con- 
verted into  vapour,  till,  at  212  degrees,  it  boils,  and  is  rapidly  expanded 
into  steam,  in  which  state  it  is  1700  times  its  original  bulk.  Steam 
can  be  still  further  expanded,  till  almost  no  known  force  is  able  to 
resist  it. 

PULVERIZE  (Lat.,  pulvus,  dust) — to  reduce  to  dust  or  powder.  Soil, 
which  is  reduced  to  small  particles  by  the  action  of  frost,  is  said  to  be 
pulverized.  So  also  of  rocks. 

DISINTEGRATE  (Lat.,  dis,  asunder,  integer,  whole) — to  break  asunder 
any  whole  or  solid  matter.  The  disintegration  of  rocks  is  caused  by 
the  slow  action  of  the  atmosphere  or  by  frosts,  &c. 

DEGRADING,  DEGRADATION  (Lat.,cte,  down,  gradus,  a  step) — to  take 
down  from  one  level  to  another.  The  degradation  of  hills  and  cliffs  is 
caused  by  rains  and  rivers  ;  hence  water  is  said  to  degrade,  or  to  exer- 
cise a  degrading  influence  on  the  land.  Degradation  and  elevation  of 
land  are  opposite  terms. 

153.  Give  an  example  of  each  mode. 

1  ?9.  Name  the  variety  of  winds  and  their  peculiarities. 

160.  What  of  the  expansion  of  water  in  freezing  T 

161.  What  is  the  extent  of  expansion  in  water  by  boiling  ? 

162.  Is  this  the  limit  of  its  expansion  1 

63.   Define  Pulverize;  Disintegrate;  Degradation;  Denudation,  8tc- 


44 


GEOLOGY. 


DENUDATION  (Lat.,  denudo,  I  lay  bare) — a  term  sometimes  employed 
as  synonymous  with  degradation,  but  inaccurately  so.  For  example, 
disintegration,  strictly  applies  to  that  action  by  which  the  materials 
of  solid  rocks  are  loosened  or  separated  from  each  other  ;  degradation 
to  the  carrying  of  these  materials  from  a  higher  to  a  lower  level ;  and 
denudation  to  the  removal  of  superficial  matter  by  water,  so  as  to  lay 
bare  the  inferior  strata. 


AQUEOUS   AGENCIES. 

53.  AQUEOUS  AGENTS,  or  those  arising  from   the  power 
and  force  of  water,  are  perhaps  not  so  universal  or  so  com- 
plex in  their  operations  as  atmospheric ;  but  they  are  more 
powerful,  and  consequently  exert  a  more  obvious  influence 
in  modifying  the  crust  of  the  globe.     Their  mode  of  action 
is  either  mechanical  or  chemical ;  mechanical,  as  when  a 
river  wears  away  its  banks,  and  carries  the  material  to  the 
sea;  and  chemical,  when,  from  gaseous  admixture,  water 
is  enabled  to  dissolve  certain  rocks  and  metals.     The  ac- 
tion of  water  is  sometimes  slow  and  gradual,  as  in  the 
wearing  down  of  rocks  by  rain ;  or  rapid  and  violent,  as  in 
the  case  of  river-floods  and  sea-storms.     The  effects  of  rain 
upon   a  cliff  may  not  amount  to  one  inch  in  a  hundred 
years,   while  hundreds  of  acres  of  alluvial   land  may   be 
swept  to  the  ocean  by  one  river  flood.    Water  operates  vari- 
ously :  sometimes  by  itself, as  in  rivers;  sometimes  in  union 
with  the  atmosphere,  as  during  land  and  sea-storms.     Its 
power  as  a  geological  agent  is  most  obvious  in  the  case  of 
rains,  springs,  rivers,  lakes,  waves,  currents,  and  tides ;  and  the 
results  of  these  agents  are  distinguished  as  meteoric,  fuvi- 
atile,  lacustrine,  or  oceanic. 

54.  Rain,  hail,  snow,  and  all  atmospheric  vapours,  exer- 
cise a  degrading  influence  on  the  earth's  surface.     By  en- 
tering the  pores  and  fissures  of  rocks,  they  soften  and  grad- 
ually dissolve   their  surface,  and  thus  materially  assist  the 


164.  What  of  aqueous  agents  ? 

165.  Name  an  instance  of  mechanical  and  one  of  chemical  action. 

166.  How  is  aqueous  action  varied? 

167.  How  may  it  be  complicated  ? 

168.  In  what  instances  is  its  power  most  obvious  ? 

169.  By  what  names  are  these  results  designated  7 

170.  Explain  the  action  of  rain  and  wind. 


AQl tOE  S    AGfeStil  Eft. 

operations  of  frosts,  winds,  &,c.  Rain,  accompanied  by 
high  winds,  acts  with  greater  force;  snow,  from  accumu- 
lating during  frost,  and  suddenly  dissolving  during  fresh 
weather,  sometimes  occasions  violent  floods  and  inunda- 
tions. Floods  arising  from  the  melting  of  snow  are  gene- 
rally very  destructive,  for,  during  the  season  when  they 
occur,  the  surface  is  soft  and  loose,  and  much  more  liable 
to  be  carried  away.  Rain  and  other  vapours  are  indispens- 
able to  the  growth  of  vegetables,  and  when  accompanied 
with  sufficient  warmth,  a  luxuriant  and  gigantic  vegetation, 
like  that  of  the  tropics,  is  the  result.  The  amount  of  rain 
which  falls  on  the  earth's  surface  is  exceedingly  varied, 
ranging  from  20  or  30  inches  to  several  feet  per  annum.  In 
tropical  regions,  rains  are  periodical ;  that  is,  fall  for  weeks 
together  at  certain  seasons.  This  gives  rise  to  inundations; 
hence  the  peculiar  phenomena  attending  the  floodings  of 
such  rivers  as  the  Nile,  Ganges,  &c. 

55.  Of  the  quantity  of  rain  which  f til  during  past  periods 
of  the  world  we  have  no  positive  knowledge:  but  if  we  are 
able  to  discover  evidence  of  a  higher  temperature,  we  are 
warranted  in  concluding  that  the  quantity  of  rain  was  much 
greater.    A  greater  fall  of  rain  would  produce  larger  rivers, 
and  larger  livers  would  carry  down  a  greater  quantity  of 
silt  and  debris ;  this  would  form  more  extensive  plains  and 
deltas ;  and  these,  again,  would  sustain  a  more  gigantic  race 
of  plants   arid  animals.     From   this  example,  the  student 
will  readily  perceive  the  connection  and  influence  of  these 
allied  causes.      Rain  water   generally    contains   carbonic 
acid,  ammonia,  and  other  substances  ;  and,  consequently, 
acts  chemically  as  well  as  mechanically. 

56.  Springs  art  discharges  of  water  from  the  crust  of  the 
earth  either  by  rents,  fissures,  or  other  openings  in  the  stir- 
face.     The  water  which  falls  in  rain,  snow,  &c.  partly  runs 
off,  and  partly  sinks  into  the  crust,  where  it  collects  in  vast 


171.  How  does  snow  operate  ? 

172.  How  is  the  vegetation  of  the  tropics  acounted  for  f 

173.  What  of  the  amount  of  rain  T 

174.  What  connection  between  temperature  and  rain  1 

175.  N'ime  the  chemical  agent  found  ia  rain. 
!"6.  Whence  are  springs  derived  T 


46  GEOLOGY. 

quantites,  and  ultimately  finds  its  way  again  to  the  surface 
by  springs.  Springs  issuing  from  strata  at  great  depths  are 
said  to  be  deep-seated;  those  from  clay  or  gravel  are  shal- 
low. Some  only  flow  during  or  shortly  after  rains,  and  are 
said  to  be  temporary;  some  flow  always,  and  are  perennial ; 
while  others  flow  and  ebb,  and  are  said  to  be  intermittent. 

57.  The  characters  in  which  geologists  have  principally 
to  consider  springs  are  cold,  thermal,  and  mineral.     Cold 
springs  have  a  mechanical  action  when  they  cut  out  chan- 
nels  for  themselves;    and  they  act  chemically  when,  for 
example,  they  contain  carbonic  acid,  and  dissolve  portions 
of  the  rocks  through  which  they  pass.  All  petrifying  springs 
— that  is,  such  as  convert  wood  and  bones  into  stony  matter 
— act  chemically.     Thermal,  or  hot  springs,  occur  in   nu- 
merous  parts  of  the  world  (England,  Iceland,  Germany, 
Switzerland,  Italy,  Hindostan,  &c.),  and  also  act  mechani- 
cally and  chemically,  but  with  much  greater  chemical  force 
than  cold  springs.     Mineral  springs  may  be  either  cold  or 
hot,  and  take  their  name  from  the  circumstance  of  their 
waters  holding  some  mineral  or  earthy  substance  in  solution. 

58.  Mineral  springs,  geologically  speaking,  are  by  far 
the  most  important,  as,  from  their  composition,  they  indicate 
the  kind  of  rocks  through  which  they  pass,  while  they  more 
or  less  influence  all  deposits  or  waters  into  which  they  flow. 
Thus,  some  contain  iron,  and  are  said  to  be  ferruginous,  or 
chalybeate;  some  copper  (cupriferous),  some  lime  (calca- 
reous), some  salt  (saline),  while  others  give  off  sulphureous 
vapours;    and  so  on   with   almost  every  known   mineral. 
Those  issuing  from  strata  containing  iron  or  lime  are  more 
or  less  impregnated  with  these  substances;  and  when  they 
arrive  at  the  surface  of  the  earth,  and  their  waters  become 
exposed  to  the  air,  the  ferruginous  or  limy  matter  is  depo- 
sited along  their  courses,  or  is  carried  down  to  the  nearest 


177.  What  variety  of  springs  are  named  ? 

178.  In  what  character  do  geologists  consider  them  7 

179.  How  do  cold  springs  act  ? 

180.  Where  are  thermal  springs,  and  what  is  their  action  ? 

181.  Define  mineral  springs. 

182.  By  what  names  are  they  called  when  they  contain  iron  ?— copper  I 

-lime  t — salt  ?  or  sulphur  ? 


,  - 

AQUEOUS    AGENCIES.  47 

river  or  lake.  If  layers  of  mud,  sand,  or  gravel  be  forming 
in  such  a  lake,  these  layers  will  be  impregnated  with  the 
matter  of  the  springs;  hence  geologists  speak  of  ferruginous, 
calcareous,  or  saliferous  strata.  Mineral  springs  may  there- 
fore be  said  to  exert  a  two-fold  influence  :  first,  by  dissolving 
and  carrying  away  matter  from  the  strata  beneath ;  and, 
second,  by  adding  that  matter  to  the  strata  which  are  now 
being  formed  on  the  surface.  The  student  will  thus  per- 
ceive the  manner  in  which  springs  act  in  modifying  the 
crust  of  the  earth  ;  and  in  proportion  to  their  size,  the  soft- 
ness of  the  strata  through  which  they  passed,  and  the  de- 
gree of  heat  they  had  acquired,  so  must  the  extent  of  their 
influence  have  been  at  any  former  period. 

59.  Rivers  are  the  most  important  aqueous  agents  em- 
ployed in  modifying  the  surface  of  the  globe.     Springs,  as 
they  issue  into  open  day,  naturally  seek  a  lower  level ;  and 
numbers  of  them   meeting  in  one  channel,  form  streams, 
which  again  join  in  some  still  lower  valley,  where  their 
union  produces  rivers  of  various  sizes.    Rivers  may  be  said 
to  be  a  species  of  natural  drainings,  by  which  the  supera- 
bundant moisture  which  falls  on  the  land  is  again  returned 
to  the  sea.     They  are  of  all  dimensions;  in  breadth  from  a 
few  feet  to  several  miles,  so  shallow  that  a  boy  might  wade 
them,  or  so  deep  as  to  float  the  largest  ships,  and  ranging 
in  length  of  course  from  fifty  or  sixty  miles  to  as  many  hun- 
dreds. 

60.  The  geological  action  of  rivers  is  twofold;  first,  by 
wearing  down  the  land  through  which  they  pass,  and  then 
by  carrying  down  the  material  to  lakes  and  seas.    Both  their 
degrading  and  transporting  force  depends  upon  their  velocity. 
For  example,  it  has  been  calculated  that  a  force  of  3  inches 
per  second  will  tear  up  fine  clay,  6  inches  will  lift  fine  sand, 
8  inches  sand  as  course  as  linseed,  and  12  inches  fine  gravel ; 


183.  What  double  influence  is  ascribed  to  mineral  springs  ? 

184.  How  may  the  extent  of  their  influence  be  estimated  ? 

185.  Into  what  do  springs  and  their  streams  flow  ? 

186.  What  of  the  variety  and  extent  of  rivers  ? 

1ST.  Upon  whit  do  the  degrading  and  transporting  effects  of  rivers  de- 
pend 1 
188.  How  is  comparative  velocity  measured  I 


48  GEOLOGY. 

while  it  requires  a  velocity  of  24  inches  per  second  to  roll 
along  rounded  pebbles  an  inch  in  diameter,  and  36  inches 
per  second  to  sweep  angular  stones  of  the  size  of  a  hen's 
egg.  Rivers,  during  floods,  often  acquire  a  much  greater 
velocity  than  this,  and  stories  of  considerable  weight  are 
then  borne  down  by  their  currents.  The  degrading  .power 
of  running-water  depends  also  upon  the  kind  of  material 
through  which  it  flows;  loose  soil,  clay,  and  sandstone  being 
easily  worn  down,  while  granite  or  basalt  will  suffer  little 
loss  for  centuries.  The  mere  flowing  of  pure  water  would 
exert  little  influence  on  hard  rocks;  but  all  rivers  carry  down 
sand  and  gravel;  and  these,  by  rubbing  and  striking  against 
the  sides  and  bottoms  of  the  channel,  assist  in  scooping  out 
those  channels  which  everywhere  present  themselves.  The 
Nerbuddah,  a  river  of  India,  has  scooped  out  a  channel  in 
basaltic  rock  100  feet  deep.  Messrs.  Sedgwick  and  Mur- 
chison  give  an  account  of  gorges  scooped  out  in  beds  of  the 
rock  called  conglomerate,  in  the  valleys  of  the  Eastern  Alps, 
600  or  700  feet  deep.  A  stream  of  lava,  which  was  vomited 
from  ^Etna  in  1603,  happened  to  flow  across  the  channel  of 
the  river  Simeto.  Since  that  time  the  stream  has  cut  a  pas- 
sage through  the  compact  rock  to  the  depth  of  between  40 
and  59  feet,  and  to  the  breadth  of  between  50  and  several 
hundred  feet.  The  cataract  of  Niagara,  in  North  America, 
has  receded  nearly  50  yards  during  the  last  40  years.  Below 
the  Falls,  the  river  flows  in  a  channel  upwards  of  150  feet 
deep  and  160  yards  wide,  for  a  distance  of  seven  miles;  and 
this  channel  has  evidently  been  produced  by  the  action  of 
the  river.  Such  effects  as  the  above  are  produced  by  the 
general  or  ordinary  action  of  water;  but  when  rivers  are 
swollen  by  heavy  rains,  by  the  sudden  melting  of  snow,  and 
the  like,  then  they  act  with  extraordinary  violence.  In 
these  cases  they  overflow  their  banks,  rush  with  a  velocity 
of  20  or  30  feet  per  second,  tear  up  the  soil,  and  sweep  be- 
fore them  trees,  animals,  houses,  and  bridges.  The  water 
of  all  rivers  which  exert  a  degrading  influence  is  more  or 


189.  What  remarkable  examples  are  cited  I 

190.  What  of  the  falls  at  Niagara  ? 

191.  What  of  the  velocity  and  force  of  freshets  T 


iCQUEOUS    AGENCIES. 


49 


less  turbid,  and  an  idea  of  their  power  may  be  formed  by 
observing  this  fact. 

61.  The  matter  which  rivers  carry  down  is  either  depo- 
sited Hong  their  banks,  in  lakes  or  in  the  ocean.     If  .they 
flow  sluggishly  along  a  flat  valley,  the  mud  and  sand  which 
their  waters  contain  gradually  falls  to  the  bottom  and  there 
rests  as  sediment.     This  sedimentary  matter  forms  what  is 
called  alluvial  land,  and  most  of  the  flat  and  fertile  valleys 
in  the  world  have  been  so  produced.     Again,  when  a  lake 
occurs  in  the  course  of  rivers,  the  sediment  is  there  col- 
lected, and  the  water  issues  from  the  lake  as  if  it  had  been 
filtered.     In  progress  of  time,  lakes  are  filled  or  silted  up 
with  this  sediment,  and  their  basins  appear  first  as  marshes, 
and  latterly  as  alluvial  land.     But   whatever  quantity  of 
matter  may  be  deposited  in  valleys  or  lakes,  the  greatest 
amount  will  always  be  carried  down  to  the  ocean,  and  de- 
posited at  the  mouth 

of  the  river  or  along 
the  shores.  The  hea- 
viest material,  such 
as  gravel,  will  fall 
down  first,  then  the 
lighter  sand,  and  ulti- 
mately the  finest  mud. 
The  mud  of  the  Gan- 
ges discolours  the 
Bay  of  Bengal  to  a 
distance  of  60  miles 
from  its  mouth  ;  and 
according  to  Captain  Sabine,  the  muddy  waters  of  the 
Amazon  may  be  distinguished  300  miles  from  the  shore. 

62.  The  consequence  of  this  continual  seaward-carriage 
of  stdimcntary  matter  is,  that  at  the  mouths  of  most  rivers 
there  are  alluvial  formations,  known  by  the  name  of  deltas; 
such  as  those  of  the  Nile,  the  Ganges,  the  Niger,  &-c. 

192.  How  is  alluvial  land  formed  ? 

193.  What  of  lakes? 

194.  What  instances  are  named  of  rivers  emptying  their  sediment  into 

the  ocean  T 

195.  What  are  deltas,  and  where  found  1 


50  GEOLOGY. 

They  take  their  name  from  their  resemblance  in  shape  to 
the  Greek  letter  A  (delta) ;  and  frequently  extend  over  vasi 
surfaces — that  of  the  Ganges  being  about  200  miles  in  one 
direction  by  220  in  another.  They  consist  of  alternate 
layers  of  sand,  gravel,  or  mud,  according  to  the  kind  of 
material  the  river  carries  down.  The  foregoing  cut  repre 
sents  the  Delta  of  the  Nile,  which  is  generally  regarded  aa 
the  type  of  all  similar  deposits. 

63.  The  geological  results  effected  by  the  agency  of  run- 
ning water  are  ceaseless  and  universal.    Rivers  are  gradually 
wearing  down  the  hills  and  higher  lands,  and  as  gradually 
silting  up  lakes  and  low  tracts  of  valley  land.     They  lay 
down  beds  of  gravel,  sand,  or  mud ;  and  these  beds,  again, 
enclose  trees,  plants,  the  bones  and  shells  of  animals,  in 
greater  or  less  abundance.     As   rivers  now  act,  so  must 
they  have  always  acted,  and  to  this  kind  of  agency  must 
we  ascribe  the  formation  of  many  of  the  rocks  (with  their 
fossils)  which  now  form  the  crust  of  the  earth  both  at  great 
depths  and  at  distances  now  far  removed  from  the  sea.    We 
have  no  actual   knowledge   of  the   rivers  of  the  ancient 
world ;  but  judging  from  the  extent  of  sedimentary  rocks, 
they  must  have  been  much  more  gigantic  than  most  of 
those  now  existing. 

64.  Waves,  currents,  and  tides  are  also  power ful  geologi- 
cal agents.   Waves  are  continually  in  action;  and  according 
to  their  violence,  and  the  materials  composing  the  sea-coast, 
so  is  the  amount  of  change  produced.     Cliffs  of  sandstone, 
chalk,  clay,  or  other  soft  rock,  are,  year  after  year,  under- 
mined by  their  force;  masses  fall  down,  are  soon  ground  to 
pieces,  and  swept  off  by  every  tide;  new  underminings  take 
place,  new  masses  fall  down,  and  thus  thousands  of  acres 
of  land  have  been  reduced  to  a  level  with  the  sea.     What 
the  waves  batter  down,  the  tides  and  currents  transport  to 
sheltered  bays  and  creeks  along  the  shore ;  so  that,  while 


196.  Whence  is  this  name  derived  ? 

197.  Of  what  do  they  consist  ? 

198.  What  of  the  uniform  and  universal  action  of  rivers? 

199.  What  geological  inferences  are  made  concerning  ancient  rivers  ? 

200.  What  instances  are  cited  of  the  effects  of  waves,  currents,  and  tides} 

201.  What  geological  reasoning  is  thence  authorized  ? 


AQUEOUS    AGENCIES'  51 

in  one  quarter  the  sea  is  making  encroachments  on  the 
land,  in  another  it  is  accumulating  sand  and  gravel  to  form 
new  land.  The  power  of  waves  and  currents  is  much  in- 
creased by  the  fact,  that  rocks  are  more  easily  moved  in 
water,  and  thus  gravel  beaches  are  piled  up  or  swept  away 
with  apparent  facility.  The  ordinary  action  of  the  sea  is 
small,  however,  compared  with  what  is  sometimes  accom- 
plished during  storms  and  high  inundations;  and  those  who 
have  witnessed  the  effects  of  a  few  successive  tides  at  such 
periods,  will  readily  form  an  estimate  of  what  may  be  ac- 
complished during  the  lapse  of  ages. 

65.  The  action  of  waves,  currents,  and  tides,  is  varied  and 
complicated;  but  it  may  be  stated  generally,  that  waves 
batter  down  the  sea-cliffs,  or  raise  up  loose  matter  from  the 
bottom ;  that  tidal  currents  convey  the  disintegrated  matter 
to  more  sheltered  bays  and  creeks;  and  that  oceanic  cur- 
rents convey  floating  material,  such  as  drift-wood,  plants, 
and  dead  animals,  from  one  part  of  the  ocean  to  another. 
Tides  rise  and  ebb  from  4  to  40  feet ;  they  enter  into  cer- 
tain rivers  for  many  miles;  and  thus  a  mingling  of  fresh 
water  and  marine,  deposits  takes  place.  As  at  present,  so 
in  ages  past;  and  by  diligently  studying  the  effects  pro- 
duced by  waves  and  tides,  the  student  will  be  enabled  to 
account  for  many  appearances  which  the  sedimentary  rocks 
present. 

EXPLANATORY    NOTES. 

THE  ACTION  OF  WATER  is  said  be  meteoric  when  it  acts  through 
the  atmosphere ;  fluviatile  (Jluvius,  a  river)  when  it  acts  by  running 
streams  or  rivers ;  lacustrine  (locus,  a  lake),  by  pools  or  lakes ;  and 
oceanic,  when  by  the  ocean. 

SILT — Mud  or  sand  carried  down  by  any  river,  and  deposited  either 
along  its  banks  or  in  lakes,  is  called  silt ;  and  when  a  lake  becomes 
filled  with  this  matter,  it  is  said  to  be  silted  up.  Silt  is  generally  ap- 
plied to  matter  calmly  or  slowly  deposited. 


202.  What  work  is  ascribed  to  waves  T 

203.  What  do  tidal  currents  effect? 

204.  How  do  oceanic  currents  operate  ? 

205.  What  is  the  varied  extent  of  the  ebb  and  flow  of  tides  f 

206.  Define  the  italicised  terms  in  the  first  Notes. 

207.  What  is  tilt ,  and  debris  >> 


52  OEOLOGY. 

DEBRIS  (French) — a  term  applied  to  the  loose  material  arising  from 
the  disintegration  of  rocks. 

ALLUVIAL  (Lat.,  luere,  to  wash,  and  ad,  together).  Land  washed  or 
brought  together  by  the  action  of  water  ia  said  to  be  alluvial.  Most 
of  the  straths  and  car'ses  in  Scotland,  and  the  dales  in  England,  are 
alluvial ;  as  are  also  the  deltas  of  all  such  rivers  as  the  Nile,  Ganges, 
Niger,  Mississippi,  &c. 

SEDIMENT  (Lat.,  sedere,  to  sit  or  settle  down) — matter  settled  down 
from  solution  in  water.  If  water  containing  mud  be  allowed  to  stand 
without  agitation,  the  mud  will  gradually  fall  to  the  bottom,  and  be- 
come sediment.  Rocks  which  have  been  deposited  after  this  manner, 
such  as  sandstone,  are  said  to  be  sedimentary. 

DEPOSIT  (Lat.,  de,  down,  and  positus,  placed) — applied  to  matter 
which  has  settled  down  from  water.  Mud,  sand,  gravel,  &c.  are  all 
deposits,  and  are  distinguished  by  the  kind  of  agency  which  produced 
them  ;  such  as  fluviatile  (river)  deposits,  lacustrine  (lake)  deposits, 
marine  (sea)  deposits,  and  littoral  (sea-shore)  deposits. 


IGNEOUS  AGENCIES. 

6ti.  Atmospheric  and  aqueous  agencies  may  be  said  to 
exert  themselves  similarly  in  modifying  the  crust  of  the 
globe.  Both  have  a  tendency  to  wear  down  the  dry  land  ; 
and  if  this  influence  went  on  year  after  year,  without  any 
counteracting  force,  a  time  might  arrive  when  hills  and 
plains  would  be  reduced  to  one  uniform  level.  But  the 
system  of  nature  is  beautifully  balanced  in  all  its  parts,  and 
as  one  set  of  agents  degrade,  another  are  employed  to  ele- 
vate. Thus  the  layers  of  loose  material  which  are  at  one 
time  spread  out  in  the  bottom  of  lakes  and  seas,  is  at  an- 
other raised  into  open  day,  to  form  new  lands  for  the  sup- 
port of  vegetable  and  animal  existence.  The  principal 
agent  employed  in  this  elevating  process  is  the  Igneous,  01 
that  which  depends  upon  some  deep-seated  source  of  fire 
Hereafter  we  shall  notice  the  opinions  which  have  been  ad 
vanced  concerning  the  origin  of  subterranean  fire ;  at  pre 
sent  we  have  merely  to  do  with  its  sensible  effects. 

67.  Igneous  agency  may  exert  itself  either  chemically  ot 
mechanically  ;  chemically,  as  in  the  production  of  new  com- 
pounds, gaseous  admixtures,  &.c.  ;t  mechanically,  as  when 


208.  Define  alluvial  with  examples,  as  also  sediment  and  deposit. 

209.  What  are  the  antagonist  agencies  called,  which  elevate  the  crus 

of  the  globe  ? 

210.  How  do  igneous  agencies  act 'chemically  and  mechanically  f 


IGXF.OUS    AGI.NC1ES. 


53 


it  elevates  and  fractures  the  solid  crust  of  the  earth.  Its 
mode  of  action  may  be  considered  under  three  heads, 
namely,  Volcanoes,  Earthquakes,  and  Gradually  Elevating 
Forces. 

68.  Volcanoes  may  be  described  as  vents  of  subterrane- 
ous fire,  through  which  smoke,  gaseous  vapours,  cinders, 
ashes,  stones,  and  rocky  matter  in  a  state  of  fusion,  are  dis- 
charged. The  explosive  or  expansive  force  of  the  internal 
fire  forms  a  vent  for  itself  in  the  first  instance;  this 
opening  is  termed  the  crater,  and  the  matter  discharged, 
gradually  collecting  around  it,  produces  a  mountain  of  a 
towering  or  conical  form,  like  that  described  by  the  follow- 
ing figure. 


View  of  Mount  jEtna. 


60.  Such  is  the  general  appearance  of  isolated  volcanoes; 
but  they  frequently  occur  in  ranges,  producing,  by  the 
union  of  their  forces,  elevated  mountain  chains  like  those 


211.  Define  a  volcano. 

212.  What  is  its  spontaneous  opening  called  ? 

213.  How  is  their  mountainous  structure  produced  1 

214.  What  of  volcanic  ranges? 

3* 


54 


GEOLOGY. 


of  South  America.  In  these  ranges,  some  of  the  vents  are 
in  active  operation,  and  others  have  become  dormant;  so  that 
we  are  insensibly  led  from  the  crater  vomiting  forth  smoke 
and  lava  to  those  now  cold  and  dormant,  and  thence  again 
back  to  distant  eras  when  all  mountain  chains  were  pro- 
duced by  the  same  kind  of  forces.  Indeed  no  one  can 
look  upon  the  mere  outward  appearance  of  ^Etna  and 
Vesuvius  on  the  one  hand,  the  Alps,  the  hills  of  central 
France,  and  the  hills  of  the  Scottish  Lowlands  on  the  other, 
without  at  once  assigning  their  origin  to  similar  causes. 

70.  Volcanic  forces  not  only  elevate  but  fracture  and  con- 
tort the  originally  plane  strata,  at  the  same  time  that  they 
throw  up  rocky  matter  which  is  not  arranged  in  distinct 
layers.  It  has  been  already  stated  that  water  has  a  ten- 
dency to  lay  down  the  material  which  it  transports  in 
flat  or  level  strata;  hence  the  sedimentary  rocks  will 
originally  partake  of  this  level  character.  Suppose,  then, 
that  the  following  engraving  represents  a  part  of  the  earth's 


crust  not  broken  or  upheaved  by  volcanic  forces,  the  same 
portion  will  present  a  very  different  appearance  when  frac- 


tured and  elevated  by  these  causes.     Here  the  sedimentary 
strata  are  not  only  thrown  out  of  their  original  level  posi- 


215.  Are  all  the  vents  in  actual  operation  7 

216.  What  geological  inference  is  thence  derived  ? 

217.  How  then  are  mountains  and  hills  to  be  accounted  for  T 

218.  Explain  the  two  diagrams,  and  the  origin  of  each. 


IGNEOUS    AGENCIES.  55 

tion,  but  are  bent,  broken  asunder,  and  in  many  places 
overlaid  by  discharges  of  volcanic  matter;  hence  a  very  ob- 
vious distinction  exists  between  rocks  of  aqueous  and  rocks 
of  igneous  origin. 

71.  A  volcano  may  at  one  time  discharge  ashes,  at  an- 
other time  rock  fragments,  and  at  a  third  molten  lava ;  and 
it  is  true  that  these  different  materials  may  be  found  on  its 
sides  arranged  in  something  like  strata;  but  they  do  not 
present   this   regularity    for   any   distance.       Sedimentary 
strata,  on  the  other  hand,  preserve  their  character  and  con- 
tinuity over  many  miles  of  country,  showing  a  calm  and 
tranquil  origin  in  comparison  with  those  masses  produced 
by  volcanic  fusion.    Other  distinctions  between  aqueous  and 
igneous  rocks  will  hereafter  be  pointed  out  to  the  student; 
but  at  present  he  cannot  fail  to  perceive  that  sand,  clay, 
mud,  and  other  matter  deposited  from  water,  must  be  more 
equally  and  flatly  laid  down  than   cinders,  ashes,  and  lava, 
which  are  vomited  forth  without  order  or  arrangement. 

72.  There  are  at  present  upwards  of  two  hundred  volca- 
noes in  active  operation.     The  greater  number  of  these  are 
to  be  found  in  the  mountain  ranges  of  South  America,  along 
the  western  coast  of  North  America,  and  in  the  Southern  Pa- 
cific.   In  central  Asia  there  are  also  several  vents;  and  ^Etna, 
Vesuvius,  and  Ilecla,  are  well  known  examples  in  Europe. 
The  number  of  active  volcanoes  is  nothing,  however,  in  com- 
parison with  what  once  existed;  for  there  is  scarcely  a  coun- 
try (Italy,  France,  Britain,  West  India  Islands,  the  Azores, 
Iceland,  &c.)  that  does  not  give  evidence  of  innumerable 
volcanic  craters  which  have  long  since  ceased  to  modify  the 
crust  of  the  globe.     Even  these  dormant  vents  are  insignifi- 
cant in  comparison  with  the  still  older  mountain  ranges  of  the 
Grampians,  Pyrenees,  Uralian,  Himmaleh,  Andes,  and  other 
chains  which   must  have  been  upheaved  by  the  same  sub- 
terranean forces. 

73.  Of  the  elevating  power  of  volcanoes  we  have  many 

219.  What  variety  in  the  volcanic  discharges? 

220.  How  \re  aqueous  and  igneous  rocks  distinguished  ? 

221.  Wher  i  are  active  volcanoes  and  how  many  ? 

222.  What  proportion  do  these  bear  to  those  now  dormant? 

223.  Name  some  of  the  examples  of  the  elevating  power  of  volcanoes. 


56  GEOLOGY. 

examples  within  the  historical  period,  and  comparing  active 
volcanic  hills  with  ancient  ranges,  we  may  arrive  at  some 
idea  of  the  enormous  power  exerted  by  igneous  forces  in 
the  earlier  ages  of  the  world.  During  an  eruption  of 
^Etna,  a  space  around  the  mountain,  150  miles  in  circum- 
ference, was  covered  with  a  layer  of  sand  and  ashes,  gene- 
rally about  12  feet  thick.  In  the  first  century,  the  cities 
of  Herculaneum  and  Pompeii  were  buried  beneath  such  a 
layer  of  matter  by  Vesuvius.  In  1660,  the  philosopher 
Kircher,  after  accurately  examining  ^Etna,  and  the  ground 
adjoining  its  base,  calculated  that  the  whole  matter  thrown 
out  by  it  at  its  various  active  periods  would  form  a  mass 
twenty  times  as  large  as  the  mountain  itself,  which  is  10,870 
feet  high,  and  30  miles  in  diameter  at  the  base.  From 
this  mountain,  in  1775,  there  issued  a  stream  of  lava  a 
mile  and  a-half  in  breadth,  12  miles  long,  and  200  feet 
thick.  At  an  earlier  period,  there  was  a  stream  which 
covered  84  square  miles.  In  1538,  a  large  hill,  since 
named  Monte  Nuovo,  was  thrown  up  in  the  neighbourhood 
of  Naples  in  one  night;  and  in  1759,  in  a  district  of  Mex- 
ico, previously  covered  by  plantations,  a  sudden  outburst 
of  volcanic  action,  which  lasted  several  months,  terminated 
in  leaving  six  hills,  varying  from  300  to  1600  feet  in  height 
above  the  old  plain.  As  on  land,  so  also  in  the  ocean ;  and 
the  student  will  hereafter  find  that  many  volcanoes  have 
been  known  to  arise  from  the  sea,  that  the  bottom  of  the 
sea  has  been  upheaved  by  the  same  influence,  and  that 
many  islands,  such  as  those  of  the  Pacific  and  Atlantic,  are 
mere  accumulations  of  volcanic  matter.  "  Owhyhee,"  says 
De  la  Beche,  "  is  a  magnificent  example  of  such  an  island; 
the  whole  mass,  estimated  as  exposing  a  surface  of  4000 
square  miles,  is  composed  of  lava,  or  other  volcanic  matter, 
which  rises  in  the  peaks  of  Mouria  Roa  and  Mouna  Kaa 
to  the  height  of  between  15,000  and  16,000  feet  above  the 
level  of  the  sea."  (See  Appendix-) 

74.  Earthquakes  are  most  important  geological  agents, 
though   their  origin  and  mode  of  action  is  scarcely  so  ob- 


224.  What  islands  are  known  to  have  this  origin  ? 

225.  Have  earthquakes  any  relation  to  volcanoes  T 


IGNEOUS    AUENCIFS.  57 

vious  as  those  of  volcanoes.  The  theories  which  have 
been  advanced  to  account  for  such  phenomena  will  be  else- 
where adverted  to;  here  it  is  sufficient  to  state,  that, though 
they  occur  in  all  parts  of  the,  world,  they  are  much  more 
frequent  and  violent  in  the  region  of  active  volcanoes. 
Earthquakes  are  strictly  mechanical  in  their  mode  of  action, 
upheaving  some  portions  of  the  crust  and  depressing  others, 
causing  rents  and  fissures,  altering  the  course  of  fivers,  ele- 
vating the  bottom  of  the  sea  to  open  day,  and  submerging 
dry  land  beneath  the  ocean.  They  are  sometimes  so  gen- 
tle in  their  operations,  that  a  slight  tremulous  motion  of 
the  earth  is  all  that  is  perceived  ;  at  other  times  the  shock 
is  so  violent,  that  the  surface  configuration  of  wide  districts 
is  completely  altered,  and  the  works  of  man  become  masses 
of  ruin.  Volumes  might  be  filled  with  accounts  of  earth- 
quakes and  their  disastrous  consequences;  we  shall  simply 
notice  a  few  historical  facts  to  show  their  importance.  In 
1596  several  towns  in  Japan  were  covered  by  the  sea;  in 
1638  St.  Euphemia  became  a  lake  ;  in  1692  Port  Royal, 
in  Jamaica,  was  submerged  ;  in  1775,  the  great  earthquake 
of  Lisbon,  sank  many  parts  of  the  Portuguese  and  African 
shores  100  fathoms  under  water;  in  1819,  at  the  mouth 
o.  the  Indus,  a  large  tract  of  country,  with  villages,  was 
submerged,  while  a  new  tract  was  elevated,  called  the 
*'  Ullah  Bund;"  in  1822  about  103  miles  of  the  Chili  coast 
was  elevated  to  the  height  of  four  or  six  I'eet ;  and  in  1843 
several  of  the  West  India  Islands  were  fearfully  convulsed, 
and  a  vast  amount  of  lile  and  property  destroyed. 

75.  The  gentral  efftct  of  earthquakes,  like  that  of  volcanic 
forces,  is  to  render  the  crust  of  the  earth  irregular  in  sur- 
face, by  depressing  some  portions  and  by  elevating  others. 
It  requires  little  effort  of  imagination  to  conceive  how  a 
level  tract  of  country  might  by  a  few  shocks,  be  converted 


226.  What  geological  changes  have  been  thus  occasioned  1 

227.  What  variety  has  been  observed  in  this  agency  ? 
22H.  What  instances  are  cited  ? 

229.  What  resemblance  in  their  general  effects  to  volcanoes  t 

230.  What  geological  changes  would  obviously  result  from  an  earth- 

qua  te. 


58 


GEOLOGV. 


into  abrupt  heights,  rents,  chasms,  and  hollows,  or  even 
sunk  many  fathoms  beneath  the  ocean.  Earthquakes  in 
the  vicinity  of  the  sea  are  generally  accompanied  with  vio- 
lent agitation  of  the  water,  and  waves  of  enormous  height 
are  rolled  upon  the  land  (60  feet  in  the  Lisbon  earthquake), 
tearing  up  the  surface,  and  forming  masses  of  loose  material. 

76.  As  earthquakes  now  act,  so  must  they  have  done  in 
all  time  past;  and  if  the  great  mountain  ranges  prove  the 
existence  of  more  extensive  volcanic  agency,  we  are  war- 
ranted to  conclude  that  earthquakes  were  also  more  frequent 
and  disastrous  in  the  earlier  ages  of  the  world.     If  fissures, 
chasms,  and  subsidences  be  at  present  produced  by  earth- 
quakes, the  student  will  have  little  difficulty  in  accounting 
for  the   numerous  rents  and  breakings  which  occur  in  the 
solid  strata  in  regions  where  volcanoes  and  earthquakes  have 

ong  since  ceased  to  exert  their  agency. 

77.  Gradually  elevating  forces  appear  to  be   intimately 
connected  with  those  which  produce  volcanic  eruptions  and 
earthquakes.     The  term  is  applied  where  we  find  tracts  of 
country  and  shores  of  the  sea  undergoing  a  slow  process  of 
elevation,  without  being  accompanied  with  any  perceptible 
violence.     Mr.  Lyell  has  discovered  instances  of  this  kind 
of  elevation  along  the  shores  of  the   Baltic,  where  places, 
which  a  century  ago  were  on  a  level  with  the  sea,  are  now 
several  feet  above  it,  and  where  even  a  change  of  a  few 
inches  has  taken  place  since  1820. 

78.  To  what  extent   such  jorces  may  have  operated  in 
times  past  we  have  no  knowledge;  and  even  at  the  present 
moment,  differences  in  the  relative  level  of  sea  and  land 
may  be  occurring  in  certain  districts  so  gradually,  that  they 
escape  our  observation.     Wherever  the  sea  has  acted  upon 
the  land  for  any  length  of  time,  it  forms  a  shore  or  beach, 
generally  an  inclined  plane,  along  which  the  tide  rises  and 
falls.     If  the  land  be  raised  up,  or  the  sea  depressed,  the 
form  of  this  beach  will  be  preserved,  and  easily  traceable 
both  from  its  level  appearance  and  Irom  the  nature  of  the 


231.  Is  it  not  rational  then  to  ascribe  such  to  this  cause? 

232.  Maj  not  gradual  elevations  be  accounted  for  in  the  same  way  1 

233.  What  evidence  is  furnished  of  such  changes  upon  the  sea-shore  ? 


ORGANIC    AGENCIES.  5^ 

gravel,  sand,  and  shells  of  which  it  is  composed.  Such 
ancient  beaches  have  been  found  in  various  parts  of  the 
world,  at  elevations  from  8  to  60  feet,  clearly  showing  that 
changes  in  the  relative  level  of  sea  and  land  have  often 
taken  place  over  vast  areas,  but  affording  little  evidence 
whether  the  changes  have  been  suddenly  or  gradually  ac- 
complished. Along  the  shores  of  the  Forth  and  Clyde  in 
Scotland,  the  east  coast  of  England,  and  the  coast  of 
France,  Portugal,  and  America,  there  is  a  very  remarkable 
beach  of  this  description,  from  40  to  50  feet  above  the 
present  sea-level,  and  presenting  a  sort  of  step  or  terrace, 
which  is  easily  traceable  sometimes  for  miles  together. 
This  terrace  is  composed  of  rounded  pebbles,  gravel,  sand, 
and  sea-shells,  and  such  material  as  usually  compose  the 
beaches  at  the  present  day. 

79.  As  some  parts  of  the  land  may  be  elevated,  so  others 
may  be  depressed;  and  consequently  we  find  stumps  of 
trees  under  the  present  sea-level,  clearly  showing  that  the 
land  on  which  they  grew  had  been  submerged.    But  whether 
these  ancient  elevations  and  depressions  have  been  accom- 
plished in  one  hour,  or  in  many  years,  whether  quietly  or 
with  violence,  geologists  have  not  yet  been  able  to  determine. 

EXPLANATORY  NOTE. 

VOLCANO,  from  Vulcan,  the  god  of  fire,  who  was  supposed  by  the 
ancients  to  reside  in  a  cavern  under  Mount  ^Etna,  and  to  forge  thun- 
derbolts for  Jupiter. 

LAVA,  an  Italian  term,  now  universally  applied  to  those  masses  of 
melted  matter  which  are  discharged  by  volcanoes  during  an  eruption. 
Loose  fragments  of  rocks,  cinders,  dust,  and  ashes,  are  comprehended 
under  the  term  scoria. 

CRATER  ((Jr.,  krater,  a  cup  or  bowl) — the  mouth  or  vent  of  a  volcano, 
so  called  from  the  resemblance  which  its  shape  bears  to  an  ancient 
drinking  bowl.  The  craters  of  volcanoes  have,  in  general,  one  edge 
a  little  lower  than  the  other,  owing  to  the  prevailing  winds  carrying 
the  greater  portion  of  the  light  material  to  the  opposite  side. 

ORGANIC    AGENCIES. 

80.  Compared  with  the  other  classes  of  agents  which 
have  been  described,  the  Organic  are  comparatively  unim- 

234.  Whence  is  the  term  volcano  derived  1 

235.  Define  lava  and  scoria. 

236.  What  of  craters? 


63  GEOLOGY. 

portant  in  modifying  the  crust  of  the  globe.  They  exert  an 
elevating  or  accumulnting  influence,  and  may  act  either  on 
the  dry  land,  in  fresh  or  in  salt  water,  according  to  the  na- 
ture of  the  vegetables  or  animals  from  which  they  result. 
They  are  comparatively  slow  in  their  operations,  but  pro- 
duce the  most  interesting  class  of  phenomena  with  which 
geological  research  has  made  us  acquainted.  Organic 
agency  presents  itself  under  two  great  heads — namely, 
Vegetable  and  Animal. 

81.  Vegetable  growth  acts  in  two  ways  :  first,  by  forming 
accumulations  of  matter,  such  as  peat;  or,  second,  by  pro- 
tecting the  soil  from   the  degrading  power  of  rains  and 
winds.     Extensive  areas  of  sand-drift  would  be  continually 
shifting,  were  it  not  for  the  vegetable  sward  which  gathers 
over  their  surface;  and  all  soils,  during  seasons  of  drought 
or  rain,  would  be  liable  to  be  blown  or  washed  away,  were 
it  not  for  the  grassy  turf  which  covers  them.    Marine  plants 
are  extremely  perishable,  and  exert  no  perceptible  influence 
on  the  earth's  crust.     Terrestrial  plants  are  of  a  very  differ- 
ent character  both  in  point  of  size,  number,  and  material  ; 
and  to  them  are  chiefly  owing  the  vegetable  deposits  in  all 
ages  of  the  world. 

82.  Trees  and  plants  are  annually  carried  down  by  rivers, 
and  deposited  along  with  the  layers  of  sand  and  mud  which 
have  already  been  noticed.     The  rafts  of  the  Mississippi 
are  frequently  several  miles  in  length,  and  from  6  to  10  feet 
thick,  being  composed  of  trees,  roots,  and  brushwood.    All 
marshes  and    shallow   waters   give    birth    to  innumerable 
aquatic  plants,  which   grow  and  decay  from  year  to  year, 
till,  in   the  course  of  centuries,  their  remains  form  thick 
accumulations  of  peat.     Peat  bogs,  of  many  miles  in  sur- 
face, and  from  4  to  20  feet  in  thickness,  are  frequent  in 
Scotland,  Ireland,  and  other  countries,  and  contain  trees 
and  the  remains  of  animals  which  once  inhabited  the  coun- 


237.  What  two  classes  of  organic  agency  are  named  ? 

238.  How  does  vegetable  growth  act  ? 

239.  Wherein  do  marine  and  terrestrial  plants  differ  ? 

240.  What  of  the  rafts  of  the  Mississippi  ? 

241.  How  does  peat  accumulate  ? 


ORGANIC    AGEWIE*.    '  61 

try.  Vegetable  growth  is  greatly  influenced  by  climate, 
being  more  prolific  and  gigantic  in  warm  than  in  cold  re- 
gions, and  being  also  entirely  different  in  character.  While, 
therefore^  peat  is  forming  in  the  bogs  of  Ireland,  the  Missis- 
sippi is  carrying  down  the  pines  of  America,  and  the  Gan- 
ges the  palms,  canes,  and  tree-ferns  of  the  Indian  jungle. 
[In  consequence  of  some  obstruction  in  the  arm  of  the 
river,  called  the  Atchafalaya,  supposed  to  have  been  formerly 
the  bed  of  the  Red  river,  a  raft  had  accumulated  in  35 
years,  which  in  1816,  was  10  miles  long,  220  yards  wide, 
and  8  feet  thick!  Although  floating,  it  is  covered  with 
living  plants,  and  of  course  with  soil.] 

b3.  Of  the  vegetation  of  past  eras  we  can  only  judge 
from  the  fossil  remains  found  in  the  solid  rocks;  and, 
comparing  that  of  the  coal  strata  with  what  now  exists,  we 
are  warranted  in  concluding  that  the  earth  has  at  certain 
times  nourished  a  more  luxuriant  and  gigantic  vegetation. 
Indeed  coal,  as  wilT  hereafter  be  shown,  is  just  as  much  .a 
mass  of  altered  plants  and  trees  as  peat  is;  and  when  the 
student  is  told  of  many  beds  of  coal  lying  one  above  another, 
some  of  which  are  ten,  fifteen,  arid  twenty  feet  in  thickness, 
he  may  readily  conjecture,  what  an  immense  mass  of  vege- 
tation has  been  compressed  into  this  one  formation.  The 
present  formation  of  vegetable  deposits,  and  the  dependence 
of  plants  upon  temperature  and  climate,  are  facts  which  it 
is  necessary  to  bear  in  mind;  otherwise  it  will  be  impossi- 
ble to  account  for  many  appearances  which  are  presented 
in  the  stratified  crust  of  the  globe. 

84.  Animal  life  is  also  an  active  agent  in  adding  to  the 
solid  material  of  the  globe.  Generally  speaking,  the  remains 
of  animals  are  very  perishable;  hence,  though  their  bones, 
teeth,  and  scaly  coverings  are  numerously  found  as  fossils, 
yet  these  form  a  mere  fraction  of  the  rocks  in  which  they 
are  imbedded.  It  is  not  in  this  light,  therefore,  that  animal 


242.  What  difference  does  climate  produce  in  vegetation  ? 

243.  What  of  fossil  remains  ? 

244.  What  of  coal  strata  ? 

245.  In  what  way  does  animnl  life  add  to  the  solid  material  of  the  globe 

to  a  limited  extent  ? 


GEOLOGY. 

existence  may  be  said  to  be  influential  in  modifying  the 
crust  of  the  earth  ;  and  we  may  reckon  of  slight  importance 
all  the  skeletons  of  the  larger  animals  which  are  deposited 
along  with  the  mud,  sand,  and  gravel  in  the  bottoms  of  ex- 
isting lakes  and  seas.  It  is  the  minutest  forms  of  life  which 
are  mainly  instrumental  in  forming  deposits  of  this  class; 
such  as  the  coral-insect,  shell-fish,  and  some  crustaceous 
animals. 

85.  By  the  labours  of  the  coral  animalcule  are  formed 
those  extensive  reefs  of  solid  coral,  or  limestone,  well 
known  to  the  navigators  of  the  Pacific.  These  reefs  rise  in 
masses  of  various  shapes  ;  sometimes  as  islets,  at  other 
times  as  circular  belts  enclosing  a  lagoon  or  lake  of  salt 
water,  but  more  frequently  in  long  abrupt  ridges  from  23 
to  100  feet  in  thickness.  The  great  reef,  which  follows 
the  line  of  the  northern  coast  of  New  Holland,  is  more  than 
1000  miles  in  length,  in  the  course  of  which  there  is  one 
continued  portion  exceeding  353  miles,  without  a  break  or 
passage  through  it.  The  animalcule  is  scarcely  so  large  as 
a  pin's  head ;  it  is  star-shaped,  is  of  a  soft  gelatinous  struc- 
ture, and  myriads,  of  them  unite  in  their  operations  to  form 
a  single  branch  of  coral.  By  examining  a  piece  of  coral, 
its  surface  will  be  found  dotted  with  small  star-like  openings, 
each  of  these  contains  a  single  animal,  and  the  space  be- 
tween them  is  covered  by  the  membrane  above  referred  to. 
These  animalcules  have  the  power  of  secreting  limy  mat- 
ter from  the  waters  of  the  ocean ;  they  are  incessantly  at 
action,  and  many  of  the  reefs  rise  several  feet  in  the  course 
of  a  few  years.  They  do  not  commence  their  labours  at 
great  depths,  but  attach  their  structures  to  rocks  from  60 
to  100  feet  below  the  surface;  and  thus  the  coral  reefs 
partake  of  the  shape  of  the  submarine  ridges  on  which  they 
are  founded.  As  their  structures  approach  the  surface,  the 
waves  and  currents  of  the  ocean  detach  large  pieces,  which 
are  either  drifted  on  the  land,  and  form  coral  beaches,  01 

246.  What  are  the  principal  forms  of  animal  life  which  are  of  impor 

tance  geologically  ? 

247.  What  remarkable  reefs  of  coral  are  named  ? 

248.  What  of  these  animalculae  and  their  labours  ? 

249.  How  are  these  reefs  elevated  above  the' surface  ? 


ORGANIC    AGENCIF.8.  63 

are  piled  upon  the  surface  of  the  growing  reef,  till  it  rises 
above  the  sea.  When  the  animal  readies  the  surface  it 
ceases  its  operations,  and  the  subsequent  elevation  into 
islands  and  dry  land  is  performed  by  the  waves  and  tides, 
and  by  the  elevating  forces  described  in  the  preceding  sec- 
tion. 

86.  Coral  is  almost  entirely  composed  of  pure  limestone, 
and  is  found  in  all  stages  of  solidity,  from  an  open  porous 
mass,  with  the  live  animal  upon  it,  to  a  hard  and  compact 
limestone,  with  scarcely  a  trace  of  its  animal  origin  discern- 
ible.    There  are  many  species  of   the  coral  animalcule, 
each  variety  rearing  its  structure  after  a  different  form;  and 
from  this  fact  such  names  have  been  given  as  tree  coral, 
fan  coral,  organ-pipe  coral,  brain  coral,  &c.      Whatever  be 
the  shape,  the  substance  formed,  and  their  mode  of  action, 
is  the  same.     They  are  found  largely  over  the   Southern 
Pacific,  in  the   Indian   Sea,  the  Red  Sea,  and  other  por- 
tions of  the  ocean.     As  at  present,  so  in   former  ages  of 
the  world  ;  and  the  student  will   hereafter  find  that  many 
of  the  beds  of   limestone  now  deep  in  the  crust  of  the 
globe,  have  been  formed   by  the  same   kind  of  organic 
agency. 

87.  Shtll-Jish,  like  the  coral  animal,  have  the  power  of 
secreting  limy  matter  from  the  ocean.     In  the  former  case, 
the  secreted  matter  forms  a  covering  or  enclosure  for  the 
animal ;  in  the  latter,  the  animal  is  external,  and  the  struc- 
ture  forms  a  mere   groundwork  for  its  operations,  and  a 
wider  field  for  the  increase  of  its  kind.    There  is  an  immense 
variety  of  shell-fish,  but  only  a  few  varieties  exist  in  great 
numbers,  and   it  is  by  the  agency  of  these  that  shell-beds 
are  formed.     The  oyster,  muscle,  and   cockle,  are   familiar 
examples;  they  live  in  great  shoals  or  beds,  covering  from  a 
few  acres  to  many  miles  of  the  bottom  of  our  seas  and  friths. 
Zoologists   have  found   that   most  shell-fish  live  in  shallow 
waters  around  the  shores;    and  from  this   habit   they  are 

250.  What  of  the  nature  and  variety  of  coral  ? 

251.  Are  there  different  species  of  animalculae  t 

252.  Where  are  they  most  numerous  ? 

253.  In  what  particulars  does  the  labour  of  shell-fish  differ  from  these  ? 

254.  Name  some  examples  of  shell-fish  who  make  these  beds. 


64 


GEOLOGY. 


more  liable  to  be  covered  by  the  material  borne  down  by 
floods  and  rivers.  In  raised  beaches,  and  in  deltas,  we 
actually  find  such  accumulations  of  shells,  sometimes  seve- 
ral feet  in  thickness,  and  presenting  the  same  appearance 
as  when  they  Jived  and  multiplied  in  the  waters.  If,  then, 
extensive  layers  of  shell-fish  now  exist,  and  if  they  are 
sometimes  found  imbedded  in  the  alluvial  matter  of  deltas 
and  lakes,  the  student  will  be  better  enabled  to  account  for 
the  occurrence  of  thick  masses  of  shells,  or  limestone 
wholly  composed  of  shells,  among  the  solid  rocky  strata. 

88.  Although  corals  and  shell-fish  are  the  most  important 
animal  agents  in  adding  to  the  material  of  the  earth's  crust, 
yet  the  exuviae  of  other  animals  must  not  be  overlooked , 
for,  it  is  often  from  the  occurrence  of  these  alone,  that  we 
are  enabled   to   infer  as  to  the   former  conditions  of  the 
world.     Thus,  the  remains  of  elephants,  lions,  and  tigers, 
may  be  carried  down  by  the  waters  of  the  Ganges,  and  de- 
posited in  its  delta;  those  of  the  rhinoceros,  hippopotamus, 
and   ostrich,  by  the  Niger;  and  those  of  the  buffalo,  elk, 
and  reindeer,  by  the  Mississippi ;  while  the  rivers  of  Bri- 
tain convey  no  such  remains  to  the   ocean.     The  sand, 
mud,  and  gravel  of  all  these  deltas  are  very  much  alike ; 
and   if  they  should    hereafter    form   rocks,  the   geologist 
could  tell  of  the  condition  of  the  country  in  which  they 
were  formed  only  by  the  kind  of  fossils  which  these  rocks 
contained. 

89.  The  formation  of  coral-reef s  and  shell-beds  is  a  grad- 
ual and  ordinary  operation  ;  but  shoals  of  other  fishes  may 
be  entombed  during  violent  storms,  or  during  submarine 
volcanic  eruptions,  which  are  attended  by  noxious  vapours, 
heat,  and  a  suffocating  agitation  of  the  mud  of  the  ocean. 
The  modes  in  which  vegetable  and  animal   life  may  affect 
the  crust  of  the  globe  are  extremely  complex  and  varied, 
but  the  above  are  the  most  obvious  and  important 


255.  What  of  the  exuviae  of  other  animals  ? 

256.  Of  what  use  are  these  in  geological  researches  ? 

257.  What  of  shoals  of  fishes,  and  how  entombed  ? 


RECAPITULATION.  DO 

RECAPITULATION. 

90.  As  detailed  in  the  preceding  section,  the  causes  chiefly- 
employed  in  modifying  the  structure  of  the  globe  may  be 
divided  into  four  classes — ATMOSPHERIC,  AQUEOUS,  IGNE- 
OUS, and  ORGANIC.  The  former  two  exert  a  degrading  or 
wasting  influence,  and  if  not  counterbalanced  by  other 
forces,  would  ultimately  wear  down  the  dry  land  to  a  level 
with  the  ocean ;  the  latter  exert  an  elevating  or  accumu- 
lating influence,  and  thus  maintain  that  elevation  and  diver- 
sity of  dry  land  essential  to  animal  and  vegetable  life.  To 
assist  the  memory,  these  agents  may  be  briefly  arranged  as 
follows : — 


DEGRADING  CAUSES. 

Atmospheric.  Aqueous. 

Winds,  Rains,  Snow,  &c. 

Frosts,  Springs, 

Heat  and  Light,  Rivers, 
Gaseous  Admix-  Waves,  Currents, 
tures.  Tides. 


ELEVATING  CAUSES. 

Igneous.  Organic. 

Volcanoes,  Vegetable  accu- 

Earthqnakes,  mulations,  as 

Gradually  ele vat-     peat,  &c. 
ing  forces.        Animal,  as    co- 
ral-reefs, shell- 
beds,  &c. 


91.  If,  then,  on  the  one  hand,  winds,  frosts,  rains,  rivers, 
and  reaves  be  continually  wasting  down  the  solid  crust,  and 
depositing  the  debris  in  layeis  along  the  bottom  of  lakes 
and  seas ;  and  if,  on  the  other,  these  layers  be  consolidated 
by  pressure,  by  chemical  processes,  or  by  heat,  and  be  then 
elevated  into  dry  land  by  volcanoes  and  earthquakes^  it 
must  be  obvious  that  the  surface  of  the  globe  is  in  a  state 
of  perpetual  change.  These  changes  may  be  slow  and  im- 
perceptible, or  sudden  and  obvious;  but  in  either  way  the 
appearances  exhibited  by  the  earth's  surface  must  be  very 
different  now  from  what  it  was  many  thousand  years  ago. 
"What  was  then  coveied  by  the  ocean,  may  now  be  dryland; 
and  what  was  dry  land,  may  have  since  been  ocean,  and 
may  now  be  dry  land  again.  These  changes  will  be  mani- 

258.  Recapitulate  the  four  classes  of  agencies  modifying  the  structure 

of  the  globe. 

259.  Repeat  the  table  in  which  they  are  arranged. 

260.  How  is  it  proved  that  the  mrface  is  perpetually  changing  T 

261.  How  must  these  changes  be  manifested  ? 


66  GEOLOGY. 

Tested  by  the  kind  of  layers  or  rocks  deposited  at  each  sue, 
cessive  period  in  the  bottom  of  the  sea ;  hence  the  geolo- 
gical history  of  the  world  can  only  be  discovered  by  the 
study  of  these  strata.  But  as  these  strata  were  upheaved 
by  volcanic  agency,  rocky  masses  of  igneous  or  volcanic 
origin  are  frequently  mingled  with  them ;  hence  we  find 
not  only  stratified  rocks  from  deposition  in  water,  but  un- 
stratified,  the  result  of  igneous  fusion.  Again,  all*  strata 
originally  deposited  by  water  will  contain  more  or  less  the 
remains  of  plants  and  animals  which  flourished  during  the 
period  they  were  deposited  ;  and  the  consideration  of  these 
petrifactions  affords  the  geologist  an  idea  of  the  kind  of  life 
which  then  peopled  the  surface  of  the  earth,  or  inhabited 
the  waters.  These  unstratified  and  stratified  rocks,  with 
the  animal  and  vegetable  remains  which  they  contain,  form 
the  solid  crust  of  the  globe — the  structure,  composition,  and 
formation  of  which  it  is  the  province  of  geology  to  consider. 

EXPLANATORY    NOTE. 

SECRETION  (Lat.,  secretus,  separated  or  set  aside).  Both  animals 
and  vegetables  are  said  to  secrete  certain  substances.  Coral,  for  ex- 
ample, is  an  animal  secretion  composed  of  lime,  which  the  animalcule 
has  the  power  of  separating  from  the  water  of  the  ocean ;  resin  and 
gum  are  vegetable  secretions. 

EXUVI.E  (Lat.,  cast  clothes).  In  Zoology  this  term  is  applied  to  the 
ejctermd  integuments  of  animals  which  are  periodically  shed  or  cast  off, 
such  as  the  skin  of  the  snake,  the  crustaceous  covering  of  the  crab, 
&c. ;  but  in  geology  it  is  employed  to  designate  fossil  animal  remains 
of  whatever  description. 

MINERAL  SUBSTANCES   COMPOSING  THE 
EARTH'S  CRUST. 

92.  THE  MINERAL  OR  ROCKY  SUBSTANCES  which  com- 
pose the  crust  of  the  globe  are  exceedingly  numerous  and 
varied.  They  are  commonly  known  by  the  name  of  rocks, 
minerals,  metals,  earths,  and  salts;  but,  geologically,  are  all 


262.  How  must  the  geological  history  be  discovered  ? 

263.  What  variety  of  strata  are  found,  and  why  ? 

264.  What  do  we  learn  from  the  petrifactions  1 

265.  Define  secretion  and  exuvia. 

266.  What  minerals  are  included  in  the  term  rock  ? 


SUBSTANCES  COMFUSINttTHE  EARTHS  CRUST. 


67 


comprehended  under  the  general  appellation  rock.  The 
individual  minerals  and  elementary  substances  of  which 
rocks  are  composed,  come  more  appropriately  under  the 
sciences  of  mineralogy,  metallurgy,  and  chemistry.  Pass- 
ing over  the  mere  surface  soil,  and  proceeding  downwards 
to  the  greatest  known  depth,  the  solid  crust  may  be  said 
to  be  composed  of  two  great  classes  of  rocks — those  ar- 
ranged in  layers,  and  those  occurring  in  irregular  masses; 
in  other  words,  the  STRATIFIED  and  UNSTRATIFIED.  The 
stratified  are  those  which  have  been  formed  from  deposition 
in  water;  hence  they  are  also  known  by  the  terms  aqueous 
and  sedimentary.  The  unstratified  are  those  which  have 
been  formed  by  fire,  and  are  also  known  by  the  terms  igne- 
ous and  volcanic.  The  following  engraving  represents  the 
appearance  which  the  stratified  and  unstratified  rocks  pre- 
sent in  a  section  of  the  earth's  crust. 


Unstratified. 


Stratified. 


93.  All  rocks,  whatever  be  th$ir  origin,  have  three  charac- 
ters under  which  they  are  viewed  by  the  geologist — namely, 
the  Mechanical,  Mineral,  and  Chemical;  and  though  it  is 
impossible,  in  an  elementary  work  of  this  kind,  to  enter 
fully  into  the  consideration  of  these  characters,  still  it  is 
necessary  that  the  student  should  be  in  some  degree  ac- 
quainted with  the  technical  terms  which  are  employed  to 
designate  these  characters. 


267.  By  what  sciences  are  they  analyzed  ? 
288.  What  two  great  classes  of  rocks  ? 

269.  How  are  the  stratified  divided  T 

270.  How  are  the  unstratified  divided  1 

271.  Under  what   three   characters  are  all   rocks  regarded  by  geolo- 

gists l 


f>3  GEOLOGY. 

94.  The  mechanical  structure  of  rucks  is  that  which  pre- 
sents itself  in  the  general  appearance  of  the   mass  as  it 
occurs  in  the  earth,  or  in  portions  of  the  mass  when  it  is 
broken  up   by  artificial  means.     It  has  nothing  to  do  with 
the  composition,  arid  merely  considers  the  appearances  pre- 
sented, whether  the  rock  be  roofing-slate,  chalk,  or  coal. 
For  example,  some  rocks  are  arranged  in  layers,  and  these 
layers  can  be  split  up  into  still  thinner  plates,  as  slate; 
others  occur  in  columns,  like  the  basalt  of  Staffa  and  the 
Giant's  Causeway ;  and  these  columns  can  be  broken  up 
into  small  prismatic  pieces.     This  structure  is  purely  me- 
chanical, and  has   been  divided  by  geologists  into  the  ex- 
ternal  and   internal— the   former  having  reference  to  the 
mere  outward  form,  and  the  latter  to  the  shape  of  the  smaller 
fragments  into  which  the  mass  can   be  broken.     The  ex- 
ternal  structure  of  coal,  for  instance,  is  stratified,  but  the 
internal  structure  varies :  caking  coal  breaking  up  into  small 
cubes  or  square  pieces,  split  coal  into  thin  slaty  divisions, 
and  cannel  coal   into  irregular  fragments,   having  a  shell- 
like  surface. 

95.  The  terms   employed  to  describe  these  varieties  of 
structure  are  useful,  in  as  far  as  they  enable  one  writer  to 
make  himself  understood  by  another.     The  following  are 
those  of  most  frequent  occurrence : — 

Massive)  occurring  in  large  masses  of  no  determinate  form,  as  gra- 
nite. 

Amorphous,  without  any  regular  shape  ;  amorphous  and  massive  are 
very  similar  terms. 

Cuboidal,  in  square  masses  resembling  cubes,  as  some  greenstones. 

Prismatic,  occurring  in  masses,  with  faces  and  angles  like  a  prism 

Columnar,  in  columns  or  pillars,  like  basalt.  Where  the  pillars  are 
not  very  distinct  and  regular,  the  term  sub-columnar  is  used. 

Stratum,  bed,  seam,  and  layer.  These  are  nearly  synonymous  terms, 
all  conveying  the  idea  of  being  spread  or  laid  out  in  parallel  masses,  as 
sandstone,  slate,  &c. 

Schistoze.  fissile,  slaty,  laminar,  are  employed  to  describe  rocks  capa- 
ble of  being  split  up  into  thin  plates  or  divisions  like  slate. 

foliated,  when  the  laminae  or  slates  split  up  into  still  thinner  leaves. 

272.  Describe  the  varieties  included  in  mechanical  structure. 

273.  Define  external  and  internal  structure  as  exemplified  in  coal. 

274.  Explain  massive  and  amorphous. 

275.  Explain  the  italicised  terms  as  defined. 


COMPOS)  NI;  Tiit  EARTH'S  CRUST.        60 

Squatnose,  when  the  fragments  have  a  scaly  appearance,  like  mica* 

Fibrous,  having  a  fibrous  texture,  like  asbestus  ;  acicular)  when  the 
fibres  have  a  distinct  needle-shaped  appearance. 

Vesicular,  cdlular,  when  the  texture  of  the  rock  is  full  of  small  cells 
er  vesicles. 

Granular,  when  the  texture  is  made  of  distinct  grains,  as  granite. 

Saccharoid,  when  the  grains  have  a  uniform  crystalline  aspect,  like 
loaf-sugar. 

Porous,  of  an  open  texture,  or  full  of  pores,  as  pumicestone. 

Friable,  when  easily  broken  down;  earthy,  of  a  soft  dull  texture;  and 
compact,  when  of  a  close  and  firm  texture. 

96.  The  mineral  character  of  rocks  has  reference  to  the 
number  and  aggregation  of  the  simple   minerals  of  which 
they  are  composed.     A  piece  of  granite,  for  example,  is 
composed  of  distinct  crystals  of  felspar,  quartz,  and  mica, 
which  are  said  to  be  simple  minerals.     In  general,  mine- 
rals occur  in  fixed  shapes,  as  cubes,  prisms,  &c.  in  the 
igneous  rocks ;  while  in  the  aqueous,  their  edges  and  an- 
gles are  broken  and  water-worn.     Some  rocks  are  simple — 
that  is,  composed  only  of  one  mineral,  such  as  limestone; 
others  compound,  or  formed  of  several  minerals,  as  granite; 
and  some,  apparently  simple,  are  in  reality  compounds  of 
several  minerals  minutely  blended  together,  as  certain  kinds 
of  sandstone, 

97.  There  are  many  hundreds  of  simple  minerals  differ- 
ing from  each  other  in  shape,  colour,  lustre,  hardness,  com- 
position, &c.     The  consideration  of  these  characteristics 
more  properly  constitute  the  science  of  mineralogy;  but  it 
is  imposible  for  the  student  in  geology  to  make  much  use- 
ful progress  without  being  acquainted  with  those  minerals 
which  enter  most  largely  into  the  composition  of  rocks. 
These  are  the  following : — 

Quartz;  the  hard  white  crystals  of  granite,  and  the  white  grains  of 
sandstone,  are  of  quartz. 

Felspar;  the  soft  grayish  crystals  of  granite,  which  can  be  easily 
scratched,  are  of  felspar. 

Mica;   the  glistening,  scaly,  and  transparent    portions  of  granite 

276.  What  are  the  simple  minerals,  as  in  granite  » 

277.  What  difference  in  shape,  and  why  f 

278.  What  examples  of  simple  and  compound  ? 

279.  How  do  simple  minerals  differ  1 

280.  Define  the  names  of  the  simple  minerals  at  her*  explained. 

4 


70  GEOLOGY. 

are  of  mica  ;  it  occurs  in  minute  scales  in  many  sandstones,  giving  to 
them  a  silvery  aspect. 

Hornblende,  a  black  or  dark-green  mineral  found  in  some  granites 
in  the  room  of  mica;  granite  is  then  called  syenite.  Hornblende  is  so 
named  from  its  horny  fracture. 

Actynolite,  so  called  from  the  pointed  or  thorny  appearance  of  its 
crystals  ;  it  is  of  a  greenish-gray  colour,  and  found  in  some  of  the  early 
slates. 

Augite,  a  greenish  mineral  found  in  many  igneous  rocks  ;  it  is  the 
type  of  a  class  to  which  the  hornblende  and  actynolite  belong'. 

Diallage,  also  called  Schiller  Spar,  an  olive,  blackish,  or  yellowish- 
green  mineral  of  a  foliated  structure,  and  having  a  metallic  lustre. 

Schorl,  occurs  in  black  prismatic  crystals  ;  is  brittle  and  lustrous, 
and  becomes  elastic  by  heat  and  friction 

Chlorite,  so  called  from  its  greenish-black  colour;  it  is  either  of 
a  crystallized  or  foliated  structure ;  and  in  the  latter  state  it  forms  the 
greater  portion  of  that  greenish  slate  called  chlorite  slate. 

Green-earth,  a  greenish  earthy  mineral  allied  to  chlorite,  which 
enters  largely  into  the  composition  of  many  trap-rocks. 

Talc,  a  transparent  mineral  resembling  mica,  but  softer,  and  not 
elastic. 

Steatite;  all  rocks  containing  this  mineral  feel  greasy  or  soapy,  and 
are  thus  easily  distinguished  ;  they  are  sometimes  called  soap-stones. 

Garnet,  a  reddish  or  wine-coloured  mineral  found  in  some  mica 
slates  and  volcanic  rocks. 

Carbonate  of  lime;  pure  marble,  chalk,  &c.are  carbonates  of  lime. 

Carbonate  of  magnesia;  lithographic  limestone  is  a  compound  of  car- 
bonate of  magnesia  and  carbonate  of  lime. 

Sulphate  of  lime;  gypsum,  or  plaster  of  Paris,  is  sulphate  of  lime. 

Chloride  of  sodium;  common  salt  is  chloride  of  sodium;  it  is  found 
in  sea-water,  and  in  masses  constituting  rock-salt. 

Bitumen,  an  inflammable  mineral,  found  either  liquid,  or  in  petro- 
leum or  rock-oil  ;  solid,  as  in  asphalte  ;  or  mixed,  as  in  common  coal. 

Iron,  oxide  and  snlphurets  of;  rust  is  an  oxide  of  iron;  pyrites,  or 
those  little  yellow  cubes  found"in  roofing-slate,  are  sulphurets. 

98.  The  most  abundant  rocks  are  formed  by  the  aggre- 
gation of  the  above  minerals.  It  would  be  impossible  to 
convey  an  adequate  idea  of  these  rocks  by  a  mere  verbal 
description  :  and  at  this  stage  the  student  should  endeavour 
to  make  himself  familiar  with  the  following  rocks  (of 
which  there  are  many  varieties),  by  the  inspection  of  actual 
specimens : — 

GRANITE,  FELSPAR   ROCK,  QUARTZ   ROCK, 

SYENITE,  CLAYSTONE,  SANDSTONE, 


281.  Repeat  the  definitions  of  minerals  here  given. 

282.  Enumerate  the  names  of  the  rocks,  formed  of  these  simple  mine- 
-  •  rals  variously  compounded. 


SUBSTANCES  COMPOSING    THK    EARTH*S  CRUST.  71 

GRENESTONE,  ORNSTONE,  CLAY-SHALE, 

BASALT,  TCHSTONE,  SLATE, 

HYFERSTHENE   ROCK,  GNEISS,  FLITTT, 

DIALLAGE   ROCK,  MICA   SCHIST.  CHERT, 

SERPENTINE,  CHLORITE   SCHIST,  LIMESTONE, 

WACKE,  HORNBLENDE   SCHIST,  COAL. 

99.  The  chemical  character  of  rocks  has  no   reference 
either  to  their  mechanical  structure  or  mineral  aggregation. 
According  to  the  deductions  of  chemistry,  all   bodies  in 
nature,  whatever  their  structure  or  appearance,  are  com- 
posed of  fifty-four  simple  or  elementary  substances.     Gra- 
nite,   mineralogically  speaking,   is   composed    of   quartz, 
felspar,  and  mica ;  but  these  three  minerals  are  each  com- 
posed of  several  chemical  elements — quartz,  for  example, 
being  a  compound  of  the  gaseous  body  oxygen,  and  a  metal 
called  silicum. 

100.  Of  the  elementary  bodies,  under  the  ordinary  pres- 
sure and  temperature  of  the  atmosphere,  there  are — 

Five  gaseous — hydrogen,  oxygen,  nitrogen,  chlorine,  and  fluorine; 

Seven  non-metallic-,  liquids  and  solids— bromine,  iodine,  sulphur, 
phosphorus,  selenium,  carbon,  and  boron  ; 

Thirteen  solid  metalloids,  which  unite  with  oxygen  to  form  the 
earths  and  alkalies — sodium,  potassium,  lithium,  aluminum,  silicium, 
yttrium,  glucium,  thorium*,  calcium,  magnesium,  zirconium,  stron- 
tium, barium ; 

Twenty-nine  metals,  which  are  all  solid  save  mercury — manganese, 
zinc,  iron,  tin,  cadmium,  arsenic,  antimony,  copper,  molybdenum, 
uranium,  tellurium,  chromium,  cerium,  nickel,  vanadium,  cobalt,  lead, 
tungsten,  titanium,  mercury,  columbium,  bismuth,  osmium,  silver, 
palladium,  rhodium,  platinum,  gold,  and  iridium. 

101.  Only  a  few  of  the  fifty-four  so-called  elements  enter 
largely   into  the  composition  or  the  rocky  masses  which 
constitute  the  crust  of  the  globe.     The  most  prevalent  are 
oxygen,  carbon,  sulphur,  aluminum,  silicium,  potassium, 
sodium,  calcium,  magnesium,  and  iron.     Of  these,  oxygen 


283.  What  of  the  chemical  character  of  rocks  T 

284.  How  many  chemical  elements  T 

285.  State  an  example  of  the  difference  between  these,  and  mineralo- 

gical  elements. 

286    Into  how  many  classes  are  the  elementary  bodies  divided  1 
287.  Name  the  most  prevalent  in  rocks. 


72  GEOLOGY. 

is  by  far  the  most  prevalent;  it  is  found  in  combination 
with  every  other  substance,  and  is  supposed  to  constitute 
fully  one-half  of  the  ponderable  matter  of  the  globe. 

102.  From  what  has  been  staled  in  the  foregoing  para- 
graphs respecting  the  mechanical,  mineral,  and  chemical 
characters  of  rocks,  it  will  be  seen  how  necessary  a  know- 
ledge of  these  is  to  the  right  investigation  of  the  constitu- 
tion of  the  earth.  It  is  true  that  geological  research  may 
be  carried  on  without  an  intimate  knowledge  of  mineralogy 
or  chemistry,  but  it  is  evident  that  a  certain  amount  of 
mineralogical  and  chemical  information  will  greatly  assist 
the  pursuit.  To  illustrate  this  by  a  familiar  example: — 
Granite,  geologically  speaking,  is  unstratified,  massive,  gra- 
nular, composed  of  several  ingredients ;  from  its  general 
structure,  it  is  regarded  as  arising  from  igneous  fusion,  and 
is  considered  as  the  basis  of  all  the  stratified  rocks.  To 
the  mineralogist  these  facts  are  of  little  importance;  he 
proceeds  to  consider  it  as  composed  of  three  distinct  mine- 
rals— quartz,  felspar,  and  mica — and  to  arrange  these  mine- 
rals into  classes  according  to  their  shape,  colour,  lustre, 
hardness,  &c.  But  a  knowledge  of  these  minerals  greatly 
assists  the  geologist;  for,  while  he  finds  them  regularly 
crystallized  in  granite,  he  finds  them  broken  and  water- 
worn  in  gneiss,  and  concludes  that  gneiss  must  have  been 
formed  of  the  disintegrated  particles  of  granite.  Again,  to 
the  chemist,  geological  conclusions  and  mineral  classifica- 
tion are  but  secondary  objects;  he  takes  up  the  simple 
minerals,  and  resolves  them  into  their  simplest  elements, 
and  finds  that  quartz  consists  of  silicium  and  oxygen;  fel- 
spar of  silica,  alumina,  lime,  potash,  oxide  of  iron,  and 
water;  mica  of  silica,  alumina,  magnesia,  potash,  oxide  of 
iron,  and  oxide  of  magnesia.  A  knowledge  of  these  che- 
mical facts  also  greatly  assists  the  geologist;  as  they  enable 
him  to  account  for  many  changes  which  take  place  among 
rocks,  and  from  whence  their  minerals  have  been  derived. 
For  instance,  iron  and  clay-slate  are  not  perceptible  in  gra- 

288.  How  is  mineralogy  shown  to  be  important  to  the  geologist  ? 

289.  What  illustration  is  cited  1 

2190.  What  of  chemical  analogies  of  quartz,  felspar,  and  mica"? 
291.  How  is  chemistry  shown  to  be  important  to  the  geologist  ? 


MEANS    OF    GEUfTUUlCAL    INVES  i'lGATlON.  73 

nite;  yet,  by  chemical  means,  the  ores  of  iron  and  clay- 
slate  may  both  be  derived  from  the  felspar  and  mica  which 
constitute  the  granite. 

EXPLANATORY  NOTE. 

CHARACTERS  OF  ROCKS. — The  student  will  readily  learn  to  distinguish 
the  mechanical  characters  of  rocks,  that  is,  that  which  relates  to  their 
external  forms  and  internal  texture.  For  example,  he  can  have  little 
difficulty  in  determining  whether  a  rock  be  columnar  or  massive, 
granular  or  fibrous  ;  he  may,  however,  frequently  be  puzzled  to  decide 
as  to  its  mineral  composition. — Certain  simple  minerals,  as  quartz, 
mica,  iron  pyrites,  &c.  are  easily  recognised ;  but  in  the  majority  of 
cases  many  tests  are  required,  such  as  taste,  smell,  adhesion  to  the 
tongue,  colour,  lustre,  form,  hardness,  and  so  on.  For  this  purpose  a 
knowledge  of  mineralogy  is  necessary  ;  an  acquirement  which,  at  this 
stage,  the  student  is  not  expected  to  possess.  It  will  therefore  be  ad- 
visable that  he  familiarize  himself  with  the  most  prevalent  minerals  and 
rocks  by  the  inspection  of  actual  specimens,  cabinets  of  which  can  be 
obtained  from  the  dealers  for  a  trifling  sum.  To  ascertain  the  precise 
chemical  constitution  of  any  rock,  is  a  matter  requiring  considerable  ex- 
perience in  the  laboratory  ;  but  possessed  of  a  retort  and  spirit-lamp, 
a  blowpipe,  a  few  test-tubes,  and  acids,  the  student  may  readily  de- 
tect the  presence  of  such  substances  as  lime,  iron,  copper,  lead,  sul- 
phur, soda,  potash,  &c. 

MEANS  OF  GEOLOGICAL  INVESTIGATION. 

103.  The  means  placed  within  man's  reach  for  investi- 
gating the  history  of  the  globe,  are  of  a  very  satisfactory  de- 
scription. The  accessible  crust  being  for  the  most  part 
formed  of  stratified  rocks  occurring  in  definite  order  one 
above  another,  each  composed  of  certain  minerals,  and 
containing  different  kinds  of  fossil  plants  and  animals,  it 
enables  us  to  determine  the  relative  time  required  for  the 
formation  of  certain  strata,  and  to  predict,  from  the  kind 
of  fossils,  what  must  have  been  the  state  of  the  earth  as  to 
climate  and  other  geographical  features  at  the  period  when 
these  remains  were  imbedded.  Strata,  for  example,  which 

292.  What  tests  are  necessary  in  deciding  the  mineral  composition  of 

rocks  T 

293.  To  what  science  do  these  belong  ? 

294'.  What  apparatus  is  necessary  for  the  chemical  analysis  of  rocks? 

295.  What  are  our  means  of  geological  investigation  T 

296.  What  are  instances  of  geological  inferences  t 


74  OF.OLOGY; 

contain  the  remains  of  marine  shells  and  fishes,  indicate 
that  they  have  been  deposited  in  seas;  those  containing 
freshwater  shells  and  plants,  that  they  have  been  formed  in 
lakes  and  estuaries ;  and  as  certain  plants  and  animals  now 
flourish  in  a  tropical  climate,  so  will  similar  fossil  remains 
indicate  that  they  have  lived  under  a  similar  temperature. 
Fine-grained  and  thinly-laminated  beds,  such  as  clay  slate, 
must  have  been  deposited  under  different  conditions  from 
a  bed  of  gravelly  conglomerate ;  and  the  circumstances 
which  went  to  the  formation  of  coal,  must  have  been  widely 
different  from  those  under  which  chalk  was  formed.  Fur- 
ther, some  strata  lie  in  a  slanting  position;  and  as  we  know 
that  all  matter  deposited  from  water  arranges  itself  in  nearly 
horizontal  beds,  these  strata  must  have  been  turned  up  by 
some  elevating  cause.  No  extensive  elevation  of  the  crust, 
however,  can  take  place  without  causing  rents  and  fractures, 
contortions,  and  oiher  dislocations  of  the  strata  ;  and  from 
the  magnitude  of  these,  some  idea  may  be  formed  of  the 
volcanic  forces  which  caused  them.  Thus  it  is,  by  the 
stratified  rocks,  the  order  in  which  they  occur,  the  kind  of 
material  of  which  they  are  composed,  and  the  organic  re- 
mains imbedded  in  them,  that  the  geologist  is  enabled  to 
proceed  with  his  investigations. 

104.  Had  the  stratified  rocks  lain  in  regular  undisturbed 
succession,  like  the  coats  of  an  onion,  man  would  have  made 
but  little  progress  in  deciphering  their  history,  as  the 
greatest  perpendicular  descent  he  has  yet  made  into  the 
crust  of  the  earth  does  not  extend  to  half-a-mile.  But  as 
these  rocks  are  thrown  up  into  slRnting  and  irregular  posi- 
tions, so  that  the  lowest  are  brought  to  the  surface  equally 
with  those  most  recently  formed,  geologists  have  been  able 
t )  collect  a  regular  series  of  stratified  rocks,  from  those  de- 
posited, as  it  were,  but  yesterday,  downwards  to  the  unstra- 
tified  granite  which  forms  their  basis.  There  are  two  great 
means  of  investigation :  artificial  sections,  as  exhibited  in 
coal-pits,  quarries,  and  tunnels  ;  and  natural  sections,  as 


297.  What  peculiarities  in  the  stratified  rocks  are  relied  on  ? 

29S.  How  are  we  enabled  to  investigate  the  deep  unstratified  rocks  ? 

299.  Define  the  two  kinds  of  sections. 


MEANS    OF    GEOLOGICAL    INVESTIGATION.  7/» 

occasionally  exposed   by  the  sea-shore,  by  ravines,  and  by 
river  channels. 

105.  Artificial  sections  assist  geological  inquiry  in  Jhi3 
manner: — Suppose  a  series  of  strata,  «,  6,  c,  d,  should  occur 
in  a  horizontal  position  (fig.  'A),  we  may  become  acquainted 


Fig.  A. 


with  their  composition  and  order  by  a  shaft  or  pit  piercing 
them;  but  by  this  means  we  cannot  arrive  at  any  great  depth 
into  the  earth's  crust,  from  the  expense  of  working  deep 
shafts,  and  the  difficulty  of  carrying  off  their  water.  Were 
the  same  series  of  rocks,  however,  thrown  up  in  a  slanting 
position  (fig.  B),  then  every  shaft  that  pierced  them  would 
*add  to  the  amount  of  our  information.  For  example,  the 
shaft  No.  1  pierces  the  coal-beds  a,  6,  and  c ;  No.  2  the 
coal-beds,  c,  d,  and  e.;  and  No.  3  the  coal-beds  e,f,  and  g. 
Now,  by  adding  the  results  of  these  comparatively  shallow 
shafts,  they  would  /urnish  us  with  information  respecting 
the  whole  series  of  strata  from  a  to  g,  and  which,  in  a 
horizontal  position,  human  means  never  could  have  reached. 
By  collecting  and  comparing  the  results  of  many  shafts  and 
borings,  geologists  are  enabled  to  map  out  sections  of  ex- 
tensive districts,  and  so  become  acquainted  with  the  struc- 
ture of  the  earth  to  enormous  depths. 

1  OH.  The  most  extensive  and  satisfactory  sections  of  stra- 
tified rocks  are  those  presented  by  ravines,  and  by  the  sea- 
shore. Thus,  in  tracing  the  course  of  a  river,  as  repre- 
sented by  the  following  engraving,  the  geologist  would 


100.  How  may  we  examine  horizontal  strata  1 
J01.  What  do  figures  A  and  B  illustrate  ? 

302.  Is  there  any  more  extensive  and  satisfactory  mode  by  a  natural 
section  1 


res 


GF.OI..C-CV. 


become  acquainted  wi.h  several   series  of  rocks,  an d  see 
their  mineral  and  fossil  characters  much  more  distinctly  than 


by  any  shaft  or  boring.  Here  the  river  bank  exposes  the  strata 
from  C  to  D  in  regular  succession,  where  it  is  obvious,  had 
they  been  in  a  horizontal  position,  only  two  or  three  beds 
would  have  been  cut  through  by  the  action  of  the  water. 
Such  sections  are  numerous  in  hilly  countries  and  along 
the  sea-coast ;  and  in  these  situations  should  the  student 
make  himself  familiar  not  only  with  the  succession  of  strata, 
but  with  the  modes  and  peculiarities  of  stratification,  which 
can  never  be  perfectly  understood  unless  from  actual  ob- 
servation. 

FORMS    OF    STRATIFICATION. 

107.  The  stratified  rocks  being,  as  it  were,  the  key  to  the* 
structure  and  history  of  the  earth,  it  will   be  necessary  to 


C  B  A 

advert  to  some  of  the  more  common  forms  in  which  strati- 


303.  What  does  figure  C  and  D  exhibit? 

304.  Where  may  such  natural  sections  be  sought? 

305.  Explain  the  variety  of  strata  in  the  first  diagram. 

306.  By  what  names  are  they  designated  ? 

307.  Describe  the  second  diagram* 


FORMS    OF    STRATIFICATION. 


77 


ficition  is  presented.  When  strata  lie  in  a  flat  or  level 
position,  they  are  said  to  be  plane  or  horizontal,  as  at  A  in 
the  subjoined  figure ;  when  they  slant,  as  at  B,  they  are  said 
to  be  inclined,  and  the  angle  which  they  form  with  the  hori- 
zon is  called  the  dip,  or  angle  of  inclination;  when  highly 
inclined,  as  at  C,  they  are  termed  vertical,  or  edge  strata, 
as  appearing  to  be  set  on  edge;  when  bent  and  twisted,  as 
at  D,  contorted;  and  when  suddenly  bent  up  by  subterra- 
nean forces,  as  at  E,  they  are  said  to  be  tilted  up. 

108.  Strata  which  dip  in  two  opposite  directions  from  a 
common  ridge,  as  at  a,  are  said  to  form  an  anticlinal  axis, 
or  saddle-back;  when  dipping  to  a  common  point,  as  at  5, 
the  axis  is  termed  synclinal,  and  the  hollow  so  formed  a 
trough  or  basin.  The  headland,  or  bluff,  formed  by  the 
abrupt  termination  of  a  series  of  strata,  is  called  an  escarp- 
ment, as  at  e ;  and  beds,  lying  apart  from  the  main  series  to 


which  they  belong  (0),  outliers.  Where  a  stratum  comes  to 
the  surface,  as  at  c,  it  is  said  to  crop  out;  and  the  part  ex- 
posed forms  the  crop  or  outcrop.  Strata  are  said  to  be  con- 
formable, when  they  are  arranged  parallel  to  each  other; 
but  unconformable  when  one  set  of  beds  overlie  a  lower 
series,  without  any  conformity  to  the  position  of  the  latter. 
The  strata  at  x  are  unconformable  to  those  upon  which 
they  rest.  There  are  several  other  terms  applied  to  the  po- 
sition and  inclination  of  stratified  masses,  but  the  above 
are  those  which  most  frequently  occur. 


308.  Define  the  italicised  technicals. 

309.  Define  conformable  and  inconformable. 


73  GBOLOGY. 

POSITIONS    OF    UNST RATIFIED    ROCKS. 

1 09.  As  all  stratified  rocks  irere  originally  laid  down  in 
a  position  nearly  horizontal,  the  different  inclinations  and 
contortions  described  above  must  have  been  produced  by 
elevating  or  igneous  causes.  Whether  the  upheaving  forces 
exerted  themselves  through  volcanic  vents,  accompanied 
by  discharges  of  unstratified  or  igneous  rock,  or  simply  as 
earthquakes,  they  would  produce  other  appearances  than 
mere  change  of  position  in  strata.  These  appearances  are 
generally  known  by  the  name  of  fractures,  or  disruptions, 
and  may  or  may  not  be  accompanied  by  discharges  of  igne- 
ous rock. 

1 10.  Discharges  ofingneous  rock  present  themselves  either 
as  disrupting,  inter  stratified,  or  overlying  masses.  In  the 
accompanying  section,  A  is  simply  a  disrupting  mass,  or 
mountain  range,  by  which  the  original  strata  are  broken 
asunder;  B  is  partly  a  disrupting  mass,  and  partly  overly- 
ing, as  it  overlies  the  strata  at  d;  and  C  is  both  disrupting 


and  interstratified,  part  of  the  fused  mass  appearing  between 
the  strata  at  e.  Disrupting  masses  are  caused  by  the  ex- 
pansive force  of  the  fused  material  from  beneath ;  overly 
ing  masses  by  the  rock  spreading  itself,  when  in  a  liquid 


310.  How  must  these  various  strata  have  been  formed  ? 

311.  What  of  fractures  and  disruptions? 

312.  What  variety  in  the  discharges  of  igneous  rock  ? 

3 1 3.  Explain  the  diagram. 

314.  How  are  disrupting  masses  produced  ? 

31. "i.   WltHt  of  ovorlving  masses,  and  iiiterstratified  ? 


POSITIONS    OP    UNSTRATIF1EI)    ROCKS.  ?'.) 

state,  over  the  surface  of  the  strata  :  and  interstratified  by 
overlying  masses  being  covered  by  a  new  deposition  of 
strata.  Sometimes  there  is  a  pseudo  or  false  inter  stratifica- 
tion; that  is,  when  the  expansive  force  of  the  igneous  rock 
has  raised  one  set  of  strata  from  another,  and  inserted  itself 
for  some  distance  between  them.  In  either  case  the  inter- 
stratified  igneous  rock  presents  no  regularity  or  continuity 
of  stratification,  and  is  easily  distinguished  from  rocks 
formed  from  sediment  in  water. 

1 1 1.  Fractures  of  the  strata  caused  by  subterranean 
forcts  are  known  by  the  terms  veins,  faults,  dykes,  slips, 
hitches,  &c.  In  the  subsequent  figure,  a  is  a  suite  of  veins 
traversing  unstratified  and  stratified  rocks;  6  a  fault,  or 
dislocation,  on  each  side  of  which  the  strata  are  thrown  at 
different  inclinations;  c  a  dyke,  composed  either  of  igne- 
ous rock  injected  from  below,  or  of  clay  and  gravel  washed 
in  from  above,  also  accompanied  by  an  alteration  of  the 
dip ;  and  d  a  hitch  or  slip  arising  from  a  portion  of  the 


strata  having  been  thrown  down  to  a  lower  level  without 
any  change  in  the  inclination.  Of  course  the  phrase  thrown 
down  is  merely  relative:  for  while  the  strata  on  the  right  of 
d  appear  to  be  thrown  down,  those  on  the  left  seem  to  be 
thrown  up.  The  mining  terms,  up-throw  and  down-throw, 
t  here  f  re,  refer  to  the  same  phenomenon,  and  are  used 
nccording  to  the  position  from  which  the  strata  happen  to 
be  viewed. 


316.  What  are  instances  of  pseudo  or  false  interstratification  T 

317.  How  are  fractures  of  strata  designated  T 

318.  Exolain  the  diagram,  and  define  the  terms. 


80  GEOLOGY. 

EXPLANATORY  NOTE. 

ANTICLINAL  (Greek,  anti,  on  opposite  sides,  and  clino,  I  bend) — 
bending  towards  opposite  sides,  such  as  strata  from  a  common  axis. 
Strata  bending  south  and  north  from  one  ridge  form  an  anticline,  or 
saddle-back  ;  but  when  they  dip  in  every  direction  from  one  point,  they 
are  said  to  be  quaquaversal, 

SYNCLINAL  (Gr.,  syn,  together,  and  clino,  I  bend) — bending  together, 
or  towards  one  point,  such  as  the  sides  of  a  basin  towards  the  bot- 
tom. 

DISRUPTING  (Lat.,<Ks,  asunder,  ruptits,  broken) — breaking  or  forcing 
asunder. 

DISLOCATION  (Lat.,  dis,  asunder,  locus,  a  place) — displaced,  or  put 
out  of  its  original  or  regular  position. 

DYKE  (Scottish,  dyke,  a  wall  or  fence) — applied  to  those  interruptions 
which  the  miner  meets  with  in  his  progress,  from  their  appearing  to 
wall  off  one  part  of  a  coal-field  from  another.  Sometimes  these  dykes 
are  only  a  few  reet  in  thickness  ;  at  other  times  they  are  as  many 
yards. 

ORYCTOLOGY— SCIENCE  OF  FOSSILS. 

(See  Oryctological  Chart.) 

{ \'2.  Fossils,  whether  vegetable  or  animal,  generally  par- 
take of  the  character  of  the  rocky  substances  in  which  they 
are  imbedded;  that  is,  if  occurring  in  limestone,  they  will 
be  more  or  less  calcareous;  if  in  coal,  more  or  less  bitu- 
minous; and  so  on  of  other  substances.  It  must  not  be 
supposed,  however,  because  a  plant  or  animal  is  found  in 
limestone,  that  it  will  be  always  wholly  calcareous,  or  be- 
cause it  is  found  in  coal,  that  it  will  be  bituminous;  the 
fact  is,  that  fossils  often  present  very  irregular  characters,  the 
organic  substance  being  sometimes  entirely  destroyed, 
leaving  only  its  cast  or  impression.  But  whatever  changes 
they  have  undergone,  they  may,  for  the  sake  of  convenience, 
be  arranged  into  three  classes;  namely,  petrifactions,  con- 
verted into  stony  matter;  bituminizations,  converted  into 
bituminous  matter;  and  metallizations,  where  the  substance 
of  the  fossil,  whether  stony  or  bituminous,  is  pervaded  by 
some  metallic  substance.  (See  Appendix.) 


319.  What  of  anticlinal  and  quaquaversal  ? 

320.  Describe  disruption,  dislocation,  and  dyke. 

321.  What  determines  the  nature  of  fossils? 

322.  Into  how  manv  elapses  are  thev  divided  t 


PETRIFACTION,  ETC.  81 

PETRIFACTION,  BITLMINIZAT1ON,  AND  METALLIZATION. 

113.  THE  PROCESS  OF  PETRIFACTION  consists  in  the  infil- 
tration of  stony  matter  into  the  pores  of  bone  or  vegeta- 
bles.    In  some  instances,  the  animal  or  vegetable  substance 
has  been  almost  entirely  dissolved,  and  the  stony  matter 
so  gradually  substituted,  that  the  petrifaction   presents  a 
perfect  resemblance  in   its  minutest  parts  to  the  original 
structure.     Petrifaction   has  been  artificially  attempted,  by 
burying  bones  in  mud,  clay,  and  lime;  when  it  was  found 
that  at  the  end  of  one  year  the  bones  had  become  harder 
and  heavier,  and  scarcely  distinguishable  from  true  fossils. 
Springs  containing  lime  in  a  state  of  chemical  solution  are 
familiar  examples  of  petrifying  agents,  when  they  convert 
pieces  of  moss,  straw,  twigs,  and  other  bodies,  into  limy  or 
calcareous  matter.     Lime  is  one  of  the  most  prevalent  petri- 
fying agencies;  but  wood  is  often  found    converted  into 
flint,  or  silicified ;  and  many  fossil  trees  are  mere  masses  of 
fine-grained  sand  or  quartz. 

114.  The  organic  structure  of  plants  and  animals  is  not 
destroyed  by  petrifaction,  as  has  been  proved   by  many  ex- 
periments.    For  example,  slices  of  fossil   trees  have  been 
made  so  thin  as  to  be  semi-transparent,  and  thus  show  the 
traces  of  vegetable  fibre ;  and   fossil  zoophytes  have  been 
suspended  in  acids  till  the  whole  of  the  lime  was  dissolved, 
leaving  the  animal  tissue  distinct  in  its  original  form,  and 
sometimes  in  its  original  colour.     From  this  it  will  be  per- 
ceived that  the   structure  of  the  organism  always  more  or 
less  remains,  and   forms  a  basis  for  the  petrifying  solution 
which   thoroughly   pervades  it,  without  disturbing  the  ar- 
rangement of  those  parts  on  which  its  characteristic  form 
depends.     It  is  this  form  or  external  character  which  ena- 
bles geologists  to  compare  and  classify  fossils  with  existing 
plants  and  animals. 

323.  In  what  does  petrifaction  consist  T 

324.  What  success  has  attended  artificial  petrifactions  1 

325.  What  kind  of  springs  will  petrify  1 

326.  Name  some  varieties. 

327.  Is  the  organic  structure  preserved  in  these  petrifaction*  ? 
32S.  Name  the  examples  which  prove  this. 

329.   Is  the  chai  *cteristic  form  important  to  geologists  T 


SiJ  GEOLOGY. 

115.  Bituminization  is  that  process  by  which  vegetables 
insensibly  lose  their  organic  structure,  and  pass  by  chemi- 
cal  process  into   bitumens;  that  is,  into  inflammable  sub- 
stances, of  which  coal,  mineral  pitch,  asphalte,  &c.  are  ex- 
amples.    Bituminization  may  sometimes  be  regarded  as  a 
sort  of  petrifaction,  as  when  substances  not  originally  vege- 
table are  impregnated  with  bituminous  matter,  such    as 
fossil  fishes  found  in  bituminous  slate.    But  bituminization 
proper  is   totally  different,  and  refers    only   to  a  certain 
change  which  vegetables  undergo,  by  which  they  more  or 
less  lose  their  vegetable  texture,  and   are  converted   into 
solid  or  liquid  bitumen.     To  render  this  more  evident  by 
analogy: — If  a   piece  of  animal  muscle  be  buried  in  the 
earth,  where  it  obtains  sufficient  moisture  and  warmth,  and 
is  wholly  excluded  from  the  air,  it  is  soon  changed  into  a 
fatty  wax-like  mass  (called  adipocere,  from  the  Latin,  adeps, 
fat,    and   cera,   wax),  in  which  no  trace  of  animal  fibre  is 
present.     In  like  manner,  if  vegetable  matter  be*excluded 
from  the  air,  and  subjected  to  heat  and  moisture,  it  is  grad- 
ually converted  into  a  black  viscous  and  inflammable  sub- 
stance, called  bitumen.     This  bitumen  is  found  in  all  states 
of  purity:  pure  and   limpid  as  naphtha,  oily  as  petroleum, 
viscous  or  slaggy  as  in  mineral  pitch  or  asphalte,  elastic  as 
in   mineral  caoutchouc,  and   solid  as   in  jet,   cannel,  and 
common  coal;  the  latter  of  which  varies  according  to  the 
quantity  of  earthy  matter  mixed   up  with  it.     Amber  and 
certain   mineral  resins  are  also  the  results  of  bituminiza- 
tion. 

116.  The  process  of  bituminization  cannot  be  fully  un- 
derstood without  a  considerable  knowledge  of  chemistry : 
a  few  of  the  changes  which  decomposing  vegetables  under- 
go may,  however,  be  enumerated.     If  vegetables  are  left 
on   the  surface  of  the  earth  exposed  to  air  arid  moisture 
they  soon  putrefy,  and   fall  down   into  a  black  pulverulent 
matter,  called  vegetable  mould.     Again,  if  they  are  sub- 


330.  Define  bituminization  with  an  example. 

331.  What  is  adipocere  ? 

332.  What  varieties  of  bitumen  are  named  ? 

333.  What  varieties  in  the  process,  and  the  different  results  f 


PETRIFACTION,  ETC.  83 

jected  to  moisture,  and  partially  excluded  from  the  atmos- 
phere, petrifaction  does  not  take  place;  but  a  half-bitumin- 
ous substance  is  formed  analogous  to  peat-moss.  Lastly, 
if  vegetable  matter  be  buried  at  depths  beyond  the  influence 
of  the  air,  neither  mould  nor  peat  is  formed,  but  bituminous 
matter  in  various  degrees  of  purity  and  perfection  is  ob- 
tained. This  process  of  bituminization  has  been  defined 
as  "  a  fermentation  peculiar  to  vegetable  matter  placed  in 
such  situations  as  not  only  to  exclude  the  external  air,  and 
secure  the  presence  of  moisture,  but  prevent  the  escape  of 
the  more  volatile  principles."  Every  one  is  familiar  with 
the  kind  of  fermentation  which  takes  place  when  half-dried 
hay  is  thrown  into  a  heap ;  it  gives  off  heat,  becomes  black 
in  colour,  and  frequently  takes  fire  and  is  consumed.  It  is 
this  heating  process  which  produces  the  bituminous  fer- 
mentation when  the  vegetable  mass  is  excluded  from  the  air, 
and  subjected  to  moisture  and  pressure.  Animal  remains 
may  be  impregnated  with  bitumen;  but  it  is  vegetables 
alone  which  can  be  converted  into  mineral  pitch,  jet,  and 
common  coal ;  and  these  substances  are  more  or  less  pure, 
according  as  earthy  matter  may  be  mingled  with  them. 

1 17.  Metallization  is  that  process  by  which  fossil  remains 
become  impregnated  with,  or  wholly  converted  into,  metal- 
lic substances.  The  student  must  be  aware  that  metals 
can  be  dissolved  or  held  in  a  state  of  solution,  as  well  as 
in  a  state  of  fusion.  In  this  state  of  solution  they  are 
borne  about  by  the  waters  which  hold  them:  and  these 
waters  either  percolate  through  the  earth,  or  mingle  inti- 
mately with  the  substances  which  compose  it.  The  strata 
which  imbed  fossils  generally  contain  metallic  substances, 
such  as  iron ;  animals  and  vegetables,  when  in  a  state  of 
decay,  give  off  certain  gases;  water  is  always  present  in 
greater  or  less  abundance;  and  thus  the  metallic  sub- 
stances, the  gases  and  water,  by  chemical  union,  form  com- 
pounds, which  enter  thoroughly  into  the  pores  of  the  fos- 

334.  Is  this  process  analogous  to  fermentation  ? 

335.  Is  it  peculiar  to  vegetables  ? 

336.  What  of  metallization  7 

337.  How  is  it  accounted  for  1 

338.  Describe  the  chemical  agents. 


84 

sils,  and  so  convert  them  into  a  metallic,  instead  of  ston) 
or  bituminous  state.  The  changes  thus  effected  are  some- 
times partial,  the  external  parts  of  the  fossil  being  metal- 
lized, whilst  the  interior  remains  stony  or  bituminous; 
sometimes  the  fossil  is  simply  covered  ever  with  an  incrust- 
ation of  metallic  salts,  such  as  iron  pyrites;  at  other  times 
the  original  elements  of  the  fossil  remain  thoroughly  im- 
bued with  the  metal;  while  not  unfrequently  the  whole  sub- 
stance is  rendered  metallic,  every  trace  of  organic  structure 
being  obliterated. 

1 18.  By  thf.se  three  processes — Petrifaction,  Bituminiza- 
tion,  and  Metallization — have   the  remains  of  plants  and 
animals,  which  once  lived   and   grew   on  the  face  of  the 
globe,  been  preserved  in  the  strata  which  compose  its  crust. 
So  complete   in  many  cases  is  this  system  of  preservation, 
that  the  geologist  is  enabled  not  only  to  discover  their  form 
and  structure,  but  to  decide  with  certainty  as  to  their  habits, 
and  to  say  whether  they  were  fresh-water  or  marine,  whether 
terrestrial    or  aquatic,  whether  they   lived  and  flourished 
under  a  tropical  or  under  a  temperate  climate. 

FOSSIL    BOTANY    AND    ZOOLOGY. 

1 19.  Before  the  geologist  be  qualified  to  decide  as  to  the 
nature  of  fossil  plants  and  animals;  before  he  can  classify 
them  and  compare  them  with  those  now  existing,  or  deter- 
mine all  the  conditions  under  which   they  must  have  flou- 
rished, he  would  require  to  be  acquainted  with  the  leading 
facts  of  botany  and  zoology.     In   an  elementary  work  of 
this  kind,  it  would  be  out  of  place  to  enter  largely  into  the 
characteristics  of  these  sciences;  but   as  a  certain  amount 
of  knowledge   is  necessary  to  the  understanding  of  subse- 
quent details,  we  may  shortly  recapitulate  the  classification 
of  plants  and  animals  as  generally  received  among  botanists 
and  zoologists.     (See  Appendix.) 

120.  VEGETABLES   may   be   arranged   under   two   grand 
divisions — CELLULAR  and  VASCULAR  : —     (Appendix.) 

339.  How  are  these  fossils  varied  ? 

340.  How  are  these  processes  and  their  products  important  to  geolo- 

gists 7 


FOSSIL    BOTANY    AND    ZOOLOG*.  85 

I.  Cellular — without  regular  Teasels,  but  composed  of  fibres  which 
sometimes  cross  and  interlace  each  other.     Conferva;,  lichens,  fungi, 
alge   (sea-weeds),  and  mosses,  belong  to  this  division.     In  some  of 
these  families  there  are  no  apparent  seed  organs. 

II.  Vascular — with  vessels  which  form  organs  of  nutrition  and  re- 
pro  luction.     According  to  the  arrangement  of  these  organs,  vascular 
plants  have  been  divided  into  four  classes: — 1.  Without  perfect  flow- 
ers, and  with  no  visible  seed  organs  (crypt ogamia).    To  this  class  many 
fossil  plants  belong ;  such  as  gigantic  tree  ferns,  horse  tails,  and  others 
resembling  ferns.     2.  With  flowers,  but  having  the  seeds  naked  (pAa- 
nerogamia  gymnospermous).    To  this  class  belong  the  cycades,  or  pine- 
apple tribe,  and  the  conifers,  or  firs.     3.  Flowering  plants  with  one 
cotyledon  or  seed-lobe  (phaner ogamia  monocotyledonous).     This  class 
comprises  water-lilies,  palms,  lilies,  the  sedge,  iris,  and  canes.     4. 
Flowering  plants  with  two  cotyledons  (phanerogamia  dicotyledonous). 
This  class  comprises  all  forest  trees  and  shrubs.     None  of  the  families 
of  plants,  but  those  in  thi$  last  class,  have  the  true  woody  structure, 
or  produce  perfect  wood,  except  the  coniferae,  or  firs  ;  but  the  wood  of 
these  is  easily  distinguishable  from  true  dicotyledonous  wood. 

121.  ANIMALS,  according  to  Cuvier,  may  be  arranged  into 
four  great  divisions — VERTEBRATED,  MOLLUSCOUS,  ARTI- 
CULATED, and  RADIATED  : — 

I.  Vertebrated — animals  which   have  a   skull  containing  the   brain, 
and  a  spine  or  back-bone  containing  the  principal  trunk  of  the  nervous 
system,  commonly  called  the  "spinal  marrow.     They  have  red  blood. 
This  division  comprehends  the  Mammalia  (those  animals  which  suckle 
their  young),  Birds,  Reptiles,  and  Fishes. 

II.  Molluscous — animals  in  this  division  have  no  internal  skeleton ; 
the  muscles  are  attached  to  the  skin,  which  in  many  species  is  covered 
with  a  shell.     The  nervous  system  and  viscera  are  composed  of  de- 
tached masses,  united   by  nervous  filaments.     They  have  a  complete 
system  of  circulation,  and  particular  organs  for  breathing  by.    Animals 
with  Bivalve,  Univalve,  and  Chambered  shells,  belonging  to  this  divi- 
sion ;  though  many  molluscs,  like  the  common  snail,  have  no  shell. 

III.  Articulated — to  this  division  belong  Worms,  Crustaceous  animals 
like  the  lobster,  and  all  insects.     Their  nervous  system  consists  of  two 
long  cords,  ranging  along  the  body,  and  swelling  out  in  different  parts 
into  knots  or  ganglions.     Worms  having  their  bodies  composed  of  rings 
are  called  annelides,  and  have  red  blood  :  some  species  of  worms  in- 
habit a  calcareous  tube,  supposed  to  be  formed  by  exudation. 

IV.  Radiated — comprises  all  those  animals  formerly  called  Zoophytes, 
or  animal-plants,  as  corallines,  &c.     In  animals  of  this  division,  the 


341.  What  sciences  are  important  in  the  study  of  fossils  1 

342.  How  are  vegetables  divided  1 

343.  Define  the  technicals  used  in  both  divisions. 
3->4.  How  are  animals  classed  7 

345.  Define  and  explain  these  terms. 
34t>.  Define  and  explain  the  technicals. 


86 


GEOLOGY. 


organs  of  sense  and  motion  are  circularly  disposed  around  a  centre  or 
axis  ;  hence  the  term  radiated,  or  disposed  in  rays.  They  have  no 
distinctly-marked  nervous  system,  and  the  traces  of  circulation  in 
many  species  can  hardly  be  discerned.  Many  of  the  radiata  are  fixed, 
such  as  the  corals  ;  others  move  and  float  about,  as  the  star-fish  and 
sea-urchin. 

122.  Besides  the  above  distinctions,  which  depend  on  the 
structure  and  form  of  plants  and  animals,  there  are  others 
which  should  constantly  be  kept  in  view ;  namely,  those 
depending  upon  mode  of  life,  climate,  and  situation.     The 
plants  of  the  tropics  are  very  unlike  those  of  polar  regions, 
both  in  number,  size,  and  character;  marine  plants  and 
animals  are  essentially  different  from  those  inhabiting  fresh 
waters;  and  aquatic  plants  and  amphibious  animals  present 
a  very  different  appearance  from  those  constantly  existing 
upon  dry  land.     Each  race  of  plants  and  animals  is,  more- 
over, perfectly  adapted   for  the  functions  it  has  to  perform 
in  the  economy  of  nature;  and   is  furnished  with  peculiar 
organs,  according  to  the  kind  of  food  upon  which  it  lives, 
and  the  other  habits  it  displays.     Thus,  one  set  of  organs 
indicates  swiftness,  another  strength,  a  third  prehensile  or 
seizing  powers,  a  fourth  climbing,  leaping,  or  swimming 
powers,  a  fifth  that  the  animal  lives  on  roots,  on  herbage, 
or  on  the  flesh  of  others. 

123.  As  in  the  vegetable  and  animal  economy  of  the  pre- 
sent day,  so  in  all  times  past;  and   thus  the  geologist,  by 
analogy  and  comparison,  is  able  to  decide  as  to  the  cha- 
racter of  the  fossil  plants  and  animals  which  he  discovers. 
He  finds  in  their  characters  and  skeletons  a  key  to  the  modes 
of  their  existence,  and  can  tell  with  precision  whether  they 
lived  in  the  waters  or  on  dry  land,  in  fresh  or  in  salt  water,  in 
a  cold  or  in  a  hot  climate ;  whether  animals  browsed  upon 
plants  or  lived  upon  other  animals,  whether  they  are  fur- 
nished with  organs  indicating  an   amphibious  existence; 
and  in  general  can  determine  their  character  and  modes  of 
existence.     Moreover,  as  certain  classes  of  plants  and  ani- 

347.  What  other  distinctions  are  important  1 

348.  How  are  the  varieties  illustrated  ? 

349.  What  of  the  permanence  of  their  economy  ? 

350.  What  are  the  points  of  geological  discovery  in  these  fossils  ? 


FOSSIL    BOTANY    AND    ZOOLOGY.  87 

mals  indicate  certain  conditions  of  the  worJd,  the  geologist 
will  be  enabled  by  their  remains  to  decipher  the  past  his- 
tory of  our  globe,  and  so  arrive  at  that  which  is  the  aim 
and  object  of  all  true  geological  research. 

EXPLANATORY    NOTE. 

PETRIFACTIONS  are,  in  general,  described  according  to  the  mineral 
substance  which  enters  most  abundantly  into  their  composition.  If 
it  be  lime,  then  they  are  designated  calcareous  (Lat.,  calx,  lime);  if 
flint,  silecious  or  silicified  (silex,  flint) ;  and  so  on  of  other  minerals. 

BITUMEN  (Gr.,  pilus,  the  pitch  tree) — a  variety  of  inflammable  mine- 
ral substances,  which,  like  pitch, "burn  with  flame  in  the  open  air. 
Naphtha,  petroleum,  and  asphaltum,  are  familiar  examples;  and  all  sub. 
stances  impregnated  with  these  bitumens  are  said  to  be  bituminous.  As 
mentioned  in  the  text,  it  is  the  prevalent  opinion  that  all  bituminous 
matter  is  of  organic  or  vegetable  origin. 

BITUMINOUS  FERMENTATION. — All  vegetable  matter  is  liable  to  cer- 
tain states  of  fermentation,  according  to  the  degree  of  heat,  air,  and 
moisture  to  which  it  is  subjected.  These  states  have  been  successively 
described  as  the  saccharine,  vinous,  acetous,  septic,  and  bituminous. 
For  example,  the  saccharine  is  that  which  manifests  itself  in  the  opera- 
tion of  malting  and  in  the  ripening  of  fruits  ;  if  water  and  heat  be  ap- 
plied, it  passes  into  the  vinous,  or  that  by  which  wine  and  spirituous 
liquors  are  formed.  Again,  if,  while  the  vinous  is  going  on,  air  be  par- 
tially admitted,  the  acetous,  or  vinegar-forming  fermentation,  will  be 
produced  ;  and  by  further  exposure  of  the  vegetable  matter  to  the  air, 
it  will  pass  into  a  mass  of  earth  and  carbon  :  this  fits  it  for  the  septic, 
or  putrefying  process;  but  if  air  be  excluded,  and  heat,  moisture,  and 
pressure  be  present,  the  bituminous  will  be  the  result.  By  a  knowledge 
of  these  processes,  it  is  easy  to  understand  how  malt,  wine,  vinegar, 
vegetable  mould,  and  coal,  are  respectively  formed. 

ADIPOCEHE  (Lat.,  adeps,  fat,  cera,  wax) — a  fatty  substance  produced 
by  the  decomposition  of  the  flesh  of  animals  in  moist  situations,  or 
under  water,  resembling,  in  some  of  its  properties,  a  mixture  of  fat  and 
wax.  It  is  found  in  damp  grave-yards,  in  peat-bogs,  where  animals 
have  been  accidentally  entombed,  and  it  is  also  occasionally  thrown  up 
on  the  sea-shore  after  a  storm.  It  has  a  chalky  aspect,  a  soapy  feel,  is 
inflammable,  and  swims  in  water. 

FOSSIL  BOTANY  AND  ZOOLOGY. — The  animals  peculiar  to  a  country 
constitute  its  Fauna,  and  the  plants  its  Flora.  The  terms  are  respec- 
tively derived  from  the  Latin  Fauni,  rural  deities,  and  Flora,  the  god- 
dess of  flowers.  As  naturalists  speak  of  the  existing  Fauna  and  Flora 
of  any  country,  so  geologists  speak  of  the  fossil  Fauna  and  fossil  Flora 
of  certain  geological  epochs  and  formations. 

351.  What  of  petrifactions  1 

352.  Give  examples  of  bitumen. 

3o3.  Name  the  varieties  of  fermentation,  and  explain  them. 

354.  Describe  adipocere,  its  nature. and  source. 

355.  What  of  the  fossil  Fauna  and  Flora  ? 


88  GEOLOGY. 

CLASSIFICATION  OF  ROCK  FORMATIONS. 

124.  The  subjects  treated  in  the  preceding  sections  may 
be   regarded   as  introductory  to  the   study  of  Descriptive 
Geology;  for,  without  a  knowledge  of  them,  it  would  be 
impossible  to  comprehend  the  nature  of  the  changes  which 
our  planet  has  hitherto  undergone.     Those  changes  are  in- 
dicated by  certain  characters  stamped  upon  the  rocks  which 
constitute  its  crust — characters  obviously  analogous  to  such 
as  are  now  produced  by  causes  in  active  operation  around 
us.     It  was  necessary,  therefore,  to  learn  something  of  the 
existing  structure  and  conditions  of  the  globe,  and  of  the 
causes — mechanical,  chemical,  and  vital — which  are  modi- 
fying these  conditions,  in  order  that  we   might  be  enabled 
to  reason  from  what  is  recent  and  apparent,  to  that  which 
has  taken  place  at  more  remote  periods. 

125.  The  term  rock  is  applied  by  geologists  not  only  to 
those  hard  substances  usually  called  so,  but  also  to  all  sands, 
clays,  gravels,  and  marls  which  occur   in  beds,   strata,  or 
masses.     It  is  also  used  to  denote  a  collection  of  such  sub- 
stances: thus,  we  say  the  "rocks  of  a  country;"  or,  speak- 
ing more  definitely  of  any  mineral  series,  we  say  the  Chalk 
rocks,  the  Carboniferous   rocks,  and    so  on.     The   rocks 
which  compose  the  crust  of  the  earth,  though  varying  much 
in  mineral  character,  as  well  as  external  appearance,  occur 
either  in  masses,  or  in  series  having  a  close  resemblance  to 
each  other ;  so  much  so,  that  geologists  conclude  that  cer- 
tain series  have  been  formed  under  similar  circumstances. 
This  opinion  is  further  confirmed  by  the  fact,  that  certain 
series  of  strata  always  imbed  fossils  of  a  different  character 
from  those  contained   in  other  series;  hence  the  origin  of 
rock  classification. 

126.  Leibnitz,   in  1680,  divided  rocks   into   two  great 
classes — STRATIFIED  and  UNSTRATIFIED — the  latter  being 
the  result  of  igneous  fusion,  and  the   former  that  of  aque- 
ous solution.     This  distinction,  though  of  importance  at 


356.  How  extensively  is  the  term  rock  applied 

357.  What  is  the  orisrin  of  rock  classification  ? 

358.  Name  that  of  Leibnitz. 


CLASSIFICATION    OF    KOCK    FORMATIONS.  83 

the  period  to  which  we  refer,  was  still  of  little  avail  in  de- 
ciphering the  history  of  the  earth,  as  unstratified  rocks  are 
mingled  with  the  highest  as  well  as  with  the  lowest  strata; 
and  as,  moreover,  the  stratified,  rocks  differ  essentially  from 
each  other,  and  often  contain  very  different  fossil  remains. 
Lehman,  a  German  mineralogist,  next  proposed  to  divide 
the  stratified  rocks  into— 

PRIMITIVE — those  containing  no  fossil  organic  remains. 
SECONDARY — those  containing  remains  of  animals  and  vegetables. 
LOCAL — those  but  partially  occurring  in  different  districts. 

127.  Werner,  the  great  German  geologist,  improved  upon 
this  classification,  and  divided  all  rocks  into  Primary,  Tran- 
sition, Secondary,  and  Local.  The  term  Transition  was 
added  by  Werner,  as  implying  that  the  rocks  so  called  ex- 
hibited a  passage  from  the  primary  into  the  secondary  in 
regard  to  their  mineral  character,  and  also  that  the  earth 
was  changing  from  an  uninhabitable  to  an  inhabitable  state 
during  the  period  of  their  formation.  Subsequently,  from 
the  fossil  discoveries  of  Cuvier  and  others,  a  more  definite 
idea  was  attached  to  the  term  Local,  and  the  word  Tertiary 
was  employed  to  denote  all  those  regularly  stratified  beds 
which  occur" above  the  Chalk  strata.  These  divisions — 
Primary,  Transition,  Secondary,  and  Tertiary — though  lia- 
ble to  many  objections,  are  still  more  or  less  in  use  by  ge- 
ologists;  hence  the  following  classification  of  the  stratified 
rocks  which  compose  the  crust  of  the  earth : — 

f  SUPERFICIAL  ACCUMULATIONS — all  loose  and  irregularly  deposited 

masses  of  clay,  sand,  gravel,  and  boulder  stones. 
I   TERTIARY — local  deposits  of  regular  strata,  containing  remains 
0;  |       of  plants  and  animals,  not  differing  widely  from  those  now  in- 
habiting the  globe. 

SECONDARY — strata  of  chalk,  clay,  and  shale,  red  and  white  sand- 
stones, coal,  ironstone,  and  limestone — occurring  in  many  parts 
of  the  world,  and  containing  fossil  plants  and  animals  of  different 
species  from  those  now  existing. 

TRANSITION — strata  of  sandstones,  shales,  slates,  and  limestones — 
containing  few  or  no  fossil  plants,  and  the  remains  of  no  higher 
animals  than  Crustacea,  shell-fish,  corals,  and  corallines. 
PRIMARY — slaty  and  crystalline  strata,  very  hard  and  compact,  and 
totally  void  of  organic  remains. 


99  GEOLOGY. 

1 28.  As  geologists  became  better  acquainted  with  the  suc- 
cession of  the  stratified  rocks,  a  more  minute  subdivision 
took  place,  and  these  formations  have  been  found  to  con- 
sist of  systems,  series,  and  groups  of  strata  differing  con- 
siderably from  each  other.  Thus  the  term  formation  is 
applied  to  designate  strata  which  seern  to  have  been  formed 
under  nearly  similar  circumstances.  A  formation  may  con- 
sist of  several  systems — that  is,  strata  having  nearly  the 
same  mineral  and  fossil  character;  and  there  may  be  seve- 
ral groups  in  a  system,  such  as  sandstone  or  limestone 
group.  All  these  groups  consist  of  strata  which,  accord- 
ing to  their  thickness  or  external  appearance,  are  desig- 
nated beds,  seams,  layers,  schists,  or  slates.  Bearing  these 
terms  in  mind,  the  student  will  be  prepared  to  understand 
the  following  table  of  stratified  rocks  as  they  occur  in  the 
British  islands  : — 


TABLE    OF    BRITISH    DEPOSITS. 

pSoiL — decomposed    vegetable    and    animal   matter, 
SUPERFICIAL  I      with  earthy  admixtures. 

A  rrrnvrTTT  A     J  ALLUVIUM —  deposits    of  sand,    gravel,    and    clay, 
TIONS  I      formed  by  the  ordinary  action  of  water. 

DILUVIUM — deposits  of  gravel  and  clay  with  bould- 
ers, formed  by  unusual  operations  of  water. 
("CRAG — calcareous  conglomerate  of  marine  shells  and 

gravel ;  beds  of  marl. 

TFRTTAR.V      <  FRESH- WATER,    OR    ESTUARY  BEDS — consisting    of 
'       ]       marls,  imperfect  limestones,  and  clays. 

I  MARINE  BEDS — consisting  of  blue  and  plastic  clays 
(^    thin  beds  of  sand,  lignite,  &c. 


359.  What  was  Lehman's  ? 

360.  How  did  Werner  improve  it  ? 

361.  For  what  purposes  did  he  apply  the  term  Transition  ? 

362.  Why  was  tertiary  substituted  for  local  ? 

363.  How  is  this  term  now  employed  ? 

364.  What  classification  is  here  adopted  ? 

365.  What  of  systems,  series,  and  groups? 

366.  How  are  the  strata  of  different  groups  designated  ? 

367    Define  every  term  used  in  this  table  of  British  deposits  1 


CLASSIFICATION    OF    ROCK    FORMATIONS. 


91 


—  soft  and  white,  with  layers  of  flint  ;  chalk, 
hard,  and  without  flints. 

Chalk        J  GAULT,  or  beds  of  bluish  marly  clays,  with  green 
System.       j       sand. 

1  GREEN-SAND  —  beds  of  green   ferruginous   sands, 

L     with  chert  nodules. 

(WEALDEN  GROUP  —  beds  of  clay,  argillaceous  lime- 

stones, and  sands. 

Oolitic       J  OOLITE  —  beds  of  oolite  limestone,  calcareous  grits, 
System.        |       sands,  and  clays,  all  calcareous. 

I  LIAS  GROUP  —  bluish  clays,  alum  shales,  marls,  and 
p     limestones,  all  finely  stratified. 
j  SALIFEROUS  MARLS  —  variegated   shales  and  shell 
New  Red  limestone,  with  bands  of  sandstone. 

Sandstone,  orJ  RED  SANDSTONE  GROUP  —  fine-grained,  sometimes 


Saliferotu 
System. 


Old  Red 

Sandstone 
r,    f 


Silurian 
System. 


j      conglomerate. 

I  MAGNESIAN  LIMESTONE  —  thick-bedded  limestones 

*-     and  calcareous  conglomerates. 

[COAL  MEASURES  —  alternating  beds  of  coal,  shale, 

ironstone,  and  sandstone. 

Carboniferous}  CARBONIFEROUS,  OR  MOUNTAIN  LIMESTONE  —  thick- 
System.  bedded  grayish  limestones  and  shales. 

J  CALCIFEROUS    SANDSTONE  —  white,    thick-bedded 

v.     sandstones,  and  calcareous  shales. 

f  YELLOW  SANDSTONES,  with  beds  of  mettled  shales 

ant^  mar^s- 
4  RED  SANDSTONES—  sometimes  fine-grained,  some- 

times  quartzose  and  conglomerate. 
j  GRAY   OR  RUSTY-COLOURED  SANDSTONES  —  micace- 
V.     ous,  and  often  iu  flags  or  thin-bedded. 
f  UPPER  SILURIAN   rocks—  gray    and    bluish    lime- 
J      stones,  with  coloured  micaceous  shales. 
j  LOWER.  SIEURIAN  rocks  —  impure  shelly  limestone, 
L     mottled  sandstones,  dark  calcareous  flags. 
^HARD   ARGILLACEOUS  rocks  —  thick-bedded  sand- 
Grduwacke  j      stones,  slaty  sandstones,  and  limestones. 
System.       j  FINE  AND  COARSE-GRAINED  slaty  rocks  —  gray  mica- 
(      ceous  slates. 

^CLAY-SLATE  —  finely  laminated  ;   dark,  liver,   and 
Clay-Slate    I      purplish-coloured. 


System. 

Mica  Schist 
System. 

Gneiss 
System. 


j  HORNBLENDE  AND  CHIASTOLITB  slates,  finely  lami- 

(^     nated. 

(  CHLORITE  SLATES — greenish-coloured  slates,  with 

^      mica,  mica  schist,  talc  schist,  crystalline  lime- 

(      stone,  and  quartz  rock. 

(  GNEISS  ROCKS — intermingled  with  irregular  beds  of 

\  quartz  rock,  crystalline  limestone,  and  mica  schist. 


To  assist  the  student  in  forming  an  idea  of  the  succession 
of  these  formations  and  systems,  the  stratified  rocks  are 
more  summarily  arranged  in  the  following  diagram  : — 

368.  Distinguish  between  formations,  systems,  series  and  groups. 

369.  Explain  all  the  technicals  of  this  table. 

370.  Observe  the  order  of  this  classification  of  the  stratified  rocks. 


GEOLOGY. 


Vegetable  Soil. 
Alluvial  Clay,  Sand,  and  Gravel. 
Diluvial  Clay  with  Boulders. 
Sandstone  and  Calcareous  Grits. 
Estuary  Marls,  Limestones,  &c. 
Blue  and  Plastic  Clays,  Marls,  &c.( 


Chalk  Beds  and  Green-sand. 
Oolite  Limestones  and  Grits. 
Lias  Limestone  and  Shales. 

Saliferous  Marls,  Shell  Lime- 
stone. 

New  Red  Sandstone. 
Magnesian  Limestone. 

Coal  Beds  alternating  with 
Sandstones,  Clay-shale, 
Ironstone,  and  impure 
Limestones. 

Mountain  Limestone. 


Old  Red  Sandstone. 
Silurian  Limestones,  &c. 
Grauwacke,  Sandy  Slates. 

Clay  Slates. 

Mica  and  Talc  Schists. 

Gneiss  Rocks,  &c. 


371.   Repeat  the  order  of  these  formations  and  systems  until  the  di- 
gram becomes  familiar. 


CLASSIFICATION    OF    ROTX    FORMATIONS.  93 

129.  The  unstratified  or  igneous  rocks  occur  in  no  regu- 
lar succession,  but  appear  amidst  the  stratified  without  order 
or  arrangement;  heaving  them  out  of  their  original  hori- 
zontal positions,  breaking  up  through  them  in  volcanic 
masses,  and  sometimes  overrunning  them  after  the  manner 
of  liquid  lava.  From  these  circumstances,  they  are  in  gen- 
eral better  known  by  their  mineial  composition  than  by 
their  order  of  occurrence.  Still,  it  may  be  convenient  to 
divide  them  into  three  great  classes;  granitic,  trappean, 
and  volcanic — granitic  being  the  basis  of  all  known  rocks, 
and  occurring  along  with  the  primary  and  transition  strata ; 
the  trappean  of  a  darker  and  less  crystalline  structure  than 
the  granitic,  and  occurring  along  with  the  secondary  and 
tertiary  rocks;  and  the  volcanic  still  less  crystalline  and 
compact,  and  of  comparatively  recent  origin,  or  still  in 
process  of  formation.  Classifying  the  stratified  and  un- 
stratified  rocks  after  this  idea,  they  would  present  the  fol- 
lowing tabular  arrangement: — 

Unstratified.  Associated  with, 

VOLCANIC        {SUPERFICIAL  ACCUMULATIONS — soil,  alluvium,  dilu- 
(      vium. 
^TERTIARY — crag,    fresh-water   marls,    London   and 

plastic  clay. 

TRAPPEAN.  ^  SECONDARY — chalk,  oolite,  Has,  new  red  sandstone, 
I  coal  measures,  mountain  limestone,  old  red  sand- 
^  stone. 

C TRANSITION — silurian  and  grauwacke  rocks,  concre- 
te A  vrrin       J      tionary  limestones. 

1U"      ',  PRIMARY— clay-slate,    crystalline    limestone,    mica 
(^     schist,  quartz,  and  gneiss  rocks* 

This  division  of  the  igneous  unstratified  rocks  subserves 
many  useful  purposes  in  geology;  at  the  same  time  that  it 
is  a  distinction  warranted  by  the  nature,  aggregation,  and 
aspect  of  their  component  minerals.  The  granitic,  so 
named  from  their  distinctly  granular  and  crystalline  tex- 


372.  What  of  the  order  of  the  unstratified  rocks  T 

373.  How  then  are  they  known  t 

374.  Into  what  three  classes  have  they  been  divided  T 

375.  Describe  each  of  these. 

376.  Repeat  the  tabular  arrangement. 

377.  What  rocks  are  comprised  in  the  granitic  T 

5 


94 


GEOLOGY. 


CLASSIFICATION    OF~  ROCK    FORMATION*.  95 

ture,  comprise  granite,  syenite,  protogine,  primitive  green- 
stone, serpentine,  porphyritic,  and  other  varieties  of  gra- 
nite. The  troppean  (Swedish,  "  trappa,"  a  stair)  are  so 
called  from  the  step-like  or  terraced  sides  of  the  hills  formed 
by  these- rocks,  which  include  basalt,  green-stone,  clink- 
stone, claystone,  trachyte,  porphyry,  and  amygdaloid.  The 
volcanic,  as  the  name  implies,  are  those  products  discharged 
by  recent  or  active  volcanoes,  such  as  lava,  obsidian,  scori®, 
pnmice,  and  tufa.  As  associated  in  the  crust  of  the 
earth,  the  Unstratified  and  Stratified  rocks  would  present 
something  like  the  opposite  section  : — 

130.  It  must  not  be  supposed,  however,  that  the  stratified 
rocks  always  occur  in  any  proportion  of  the  earth's  crust 
in  full  and  complete  succession,  as  represented  above ;  all 
that  is  meant  is,  that  such  would  be  their  order  if  every 
group  and  formation  were  present.  But  whatever  number 
of  groups  may  be  present,  they  never  happen  out  of  their 
regular  order  of  succession ;  that  is,  clay-slate  never  oc- 
curs above  coal,  nor  coal  above  chalk.  Thus  at  London, 
tertiary  strata  occupy  the  surface ;  in  Durham,  magnesian 
limestone;  in  Fife,  the  coal  measures;  and  in  Perthshire, 
the  old  red-stone  and  clay-slate;  so  that  it  would  be  fruit- 
less to  dig  for  chalk  in  Durham,  for  magnesian  limestone 
in  Fife,  or  for  coal  in  Perthshire.  It  would  not  be  absurd, 
however,  to  dig  for  coal  in  Durham,  because  that  mineral 
underlies  the  magnesian  limestone;  or  for  old  red  sand- 
stone in  Fife,  because  that  formation  might  be  naturally 
expected  to  occur  under  the  coal  strata  of  that  county,  in 
the  regular  order  of  succession.  To  make  this  order  of 
succession  still  plainer,  suppose  the  rock  systems  to  be  re- 
presented by  series  of  figures,  we  might  have — 


379.  Whafcin  the  trappeanT 

380.  What  in  the  volcanic  ? 

381.  Do  the  strati6ed  rocks  always  occur  in  full  and  complete  succes- 

sion, or  only  in  this  order  when  present  I 

382.  What  variety  in  illustrated  T 


96  GFOI.OOT. 

7" 

6 

5 

4 

3 

2 

U          LI. 

Any  member  of  the  series  may  be  absent ;  but  those  that 
remain  never  occur  out  of  their  natural  order  of  suprapo- 
sition. 

EXPLANATORY    NOTE. 

CLASSIFICATION  OF  ROCKS.— Other  "  Systems  of  Classification"  than 
the  above  have  from  time  to  time  been  advanced  by  geologists  ;  but 
as  most  of  them  are  founded  upon  some  favourite  theory,  or  upon 
mere  local  data,  they  have  not  met  with  any  thing  like  a  general  re- 
ception. It  may  be  necessary,  however,  to  notice  some  of  the  dis- 
tinctions which  occur  in  the  works  of  certain  modern  authors.  Cony- 
beare  and  Phillips,  in  their  Geology  of  England  and  Wales,  divide  the 
stratified  crust  into  the  following  orders  : — 

1.  Superior — containing  the  Tertiary  deposits. 

2.  Supermedial — comprising  the  chalk,  oolite,  and  new  red  sand- 
stone. 

3.  Medial — comprising  the  coal  measures,  mountain  limestone,  and 
old  red  sandstone. 

4.  Submedial~conta.in\ng  the  Transition  strata. 

5.  Inferior — embracing  all  the  Primitive  formations. 

Others  have  proposed  to  divide  the  crust  into  five  great  formations  ; 
namely,  Colluvial,  Cretaceous,  Carboniferous,  Schistose,  and  Crystal- 
line ;  each  of  these  formations  being  subdivided  into  three  systems. 
Subdivided  in  this  manner,  the  carboniferous  and  cretaceous  would 
present  the  foil  owing  arrangement : — 

Super  cretaceous — plastic  clays,  marls,  and  lignite  beds  (Tertiary). 
Cretaceous — chalk,  chalk  marls,  and  green-sand. 
Subcretaceous — weald,  oolite,  and  lias  strata. 

Super  carboniferous — variegated  marls,  red  sandstone,  and  magne- 
sian  limestone. 

Carboniferous — coal  measures,  millstone,  and  mountain  limestone. 
Subcarboniferous — old  red  sandstone. 

The  rocks  of  the  stratified  crust,  divided  and  subdivided  in  this  man- 
ner, are  easily  remembered ;  the  arrangement,  moreover,  being  one 


383.  Explain  the  series  of  figures. 

384.  What  of  supraposition,  and  its  value  to  the  geologist  } 

385.  What  other  classifications  have  been  proposed  I 


GRANITIC    BASIS    OF    PRIMARY     STRATA.  97 

which  is  warranted  by  actual  observation.  The  term  fossiliferoiu  is 
commonly  employed  to  denote  all  those  formations  in  which  fossils 
have  been  found ;  and  non-fossil if 'erous,  those,  like  the  mica  schist  and 
gneiss,  in  which  no  organic  remains  have  yet  been  discovered.  Meta- 
morphic  is  sometimes  applied  to  those  non-fossiliferous  systems,  imply- 
ing that  the  strata  have  been  so  metamorphosed  by  heat,  as  to  oblite- 
rate all  traces  of  fossil  exuviae.  Mr.  Lyell  divides  the  tertiary  strata 
into  foar  groups;  namely, Eocene,  Meiocene,  Pleiocene,  and  Pleistoctnt; 
these  terms  indicating  the  approach  which  the  imbedded  fossils  make 
to  existing  nature.  For  example,  Eocene  (Gr.,  eos,  the  dawn,  and  kai- 
*o*,  recent),  indicates  those  strata  in  which  the  dawn  or  commence- 
ment  of  recent  animals  takes  place;  Meiocene  (melon,  less),  less 
recent ;  Pleiocene  (pleion,  more),  more  recent;  and  Pleistocene  (pleis- 
ton,  most  recent,)  or  approaching  nearly  to  existing  orders.  Instead  of 
Stratified  and  Unstratined,  or  Sedimentary  and  igneous,  some  geolo- 
gists make  use  of  the  terms  Neptunian  and  Plutonic — the  former  being 
derived  from  Neptune,  the  god  of  the  sea  or  water,  and  the  latter  from 
Pluto,  the  god  of  fire. 


GRANITIC  BASIS  OF  PRIMARY  STRATA. 

.131.  We  commence  our  investigation  of  the  earth's 
crust,  by  describing  the  lowest  or  earliest  formations  of 
strata.  Some  geologists  in  their  descriptions  begin  at  the 
surface,  and  proceed  downwards;  but  it  is  certainly  the 
more  natural  and  intelligible  method  to  commence  with 
the  lowest,  and  proceed  upwards — seeing  that  the  lowest 
have  been  deposited  first,  and  that  each  succeeding  forma- 
tion must  have  been  formed  from  the  disintegrated  mate- 
rials of  those  which  preceded  it. 

1 32.  Whatever  may  have  been  th*  origin  of  the  globe, 
we  are  warranted  in  stating  that  GRANITIC  ROCKS  form  a 
solid  crust  or  basis  upon  which  all  the  systems  of  strata 
rest  These  granitic  rocks  show  no  traces  of  stratification; 
they  are  all  highly  crystalline;  none  of  their  crystals  are 
water-worn  ;  and  from  these  circumstances,  as  well  as  from 
the  fact  that  we  find  them  bursting  up  through,  and  displac- 
ing the  primary  strata,  it  is  concluded  that  they  are  of  ig- 
neous origin.  If  ever  this  globe  was  in  a  fused  state,  as 


3^6.  What  additional  classifications  are  spoken  of? 

3>7.  Why  do  we  begin  at  the  lowest  strata  and  proceed  upward  f 

3S8.  What  may  be  regarded  as  the  basis  of  the  earth's  crust  f 

389.  Whence  have  we  the  evidence  of  their  igneous  origin  f 


98  GEOLOGY. 

has  been  supposed  by  many  philosophers,  the  granitic  crust 
is  such  as  would  be  formed  by  cooling  down  of  the  igneous 
matter.  Cooling  and  contracting  irregularly,  it  would 
assume  an  unequal  surface;  here  forcing  itself  up  into 
considerable  heights,  and  there  sinking  into  hollows;  the 
highest  granitic  mountains  bearing  no  greater  proportion 
to  the  size  of  the  globe,  than  the  blisters  and  scorias  on  a 
smelting  furnace  do  to  the  liquid  mass  upon  which  they  are 
formed. 

1 33.  The  composition  of  granitic  rocks  is  somewhat  varied. 
Granite  proper  is  composed  of  crystals  of  felspar,  quartz, 
and  mica;  is  generally  of  a  grayish  colour;  but  is  some- 
times reddish,  from  the  oxide  of  iron  contained  in  the  fel- 
spar. When  the  dark  glistening  mineral  hornblende  takes 
the  place  of  the  mica,  the  rock  is  known  by  the  name  of 
Syenite,  from  Syene  in  Egypt,  where  it  is  found  in  great 
abundance;  arid  when  talc  supplants  the  mica,  the  admix- 
ture of  felspar,  quarlz,  and  talc,  forms  the  Protogine  of 
French  geologists.  Sometimes  it  is  formed  by  an  admix- 
ture of  quartz  and  hypersthene,  with  scattered  crystals  of 
mica,  and  is  then  called  hyprrsthenic  granite;  or  it  may 
assume  a  speckled  and  mottled  appearance,  from  the  pre- 
sence of  variously-coloured  minerals,  such  as  chlorite,  and 
is  then  called  serpentine,  from  the  fanciful  resemblance  it 
bears  to  the  serpent's  skin.  [At  New  Haven  and  Milford, 
in  Connecticut,  a  beautiful  variety  of  this  rock  is  found, 
which  is  called  verd-antique  marble.  It  is  a  mixture  of 
serpentine  with  limestone,  talc,  hornblende,  and  felspar,  and 
exists  in  several  varieties.]  Porphyritic  granite  is  also  of 
common  occurrence  ;  that  is,  when,  in  addition  to  the  crys- 
tals which  compose  the  general  mass,  larger  crystals  of 
felspar  are  indiscriminately  mingled  through  it.  Occasion- 
ally, the  minerals  in  granite  are  so  arranged  as  to  bear  a 
resemblance  to  the  lines  in  Arabic  writing;  hence  this 
variety  is  known  by  the  name  of  graphic  granite. 


390.  How  do  the  granitic  rocks  render  it  probable  that  the  globe  was 

once  in  a  state  of  fusion,  or  liquefaction  by  heat  J 

391.  Of  what  elements  is  granite  composed? 

392.  When  does  it  become  Syenite  ? 

393.  What  is  Protogine  7 


GRANITIC    BASIS  OF  PR1MAKV  STRATA.  99 

134.  Besides  the  above  varieties,  there  are  other  distinc- 
tions in  use  among  geologists,  according  to  the  colour  and 
composition  of  granitic  rocks.  Felspar,  quartz,  mica,  horn- 
blende, and  hypersthene,  are  the  most  abundant  constitu- 
ents; but  the  aspect  of  the  mass  is  sometimes  modified  by 
the  partial  admixture  of  other  minerals,  especially  actyno- 
lite,  chlorite,  talc,  sch'orl,  and  steatite.     When  only  two 
minerals  form  a  granitic  rock  (as  felspar  and  mica),  it  is 
called  a  binary  granite. ;  when  three  (felspar,  quartz,  and 
mica),  a  ternary  granite;  and  when  four  (quartz,  mica,  fel- 
spar, and  hornblende),  a  quaternary  granite. 

135.  The  structure  of  granite  is  always   massive  and 
irregular;  its  texture  is  of  various  degrees  of  fineness,  from 
a  hard  and  close-grained  rock,  to  a  coarse  and  loose  aggre- 
gation of  primary  crystals. 

136.  The  position  and  relation  of  granite  to  the  primary 
strata  is  exceedingly  irregular.     Sometimes  it  rises  up  in 
mountain  masses  (ra  w),  at  other  times  spreads  out  as  an 
undulating  floor  or  basis  (6  6),  and  not  unfrequently  breaks 
through  the  unstratified  rocks  in  veins  (v  v  v  v  v)  of  the 


b  b 

Relative  Positions  of  Granite. 

most  fantastic  description.  From  these  facts,  there  can  be 
no  doubt  of  its  igneous  origin  ;  and  the  student  will  there- 
fore be  prepared  to  find  it,  like  all  other  igneous  rocks, 
occurring  amid  the  stratified  formations  at  various  periods 
of  the  earth's  history.  Generally  speaking,  it  is  associated 
with  the  primary  and  transition  formations,  just  as  trap 

394.  What  is  the  nature  of  other  varieties,  and  how  designated  ? 

395.  Give  examples  of  binary,  ternary,  &c. 

396.  Explain  how  the  diagram  proves  the  igneous  origin  of  granite. 

397.  Is  it  ever  found  associated  with  all  the  formations  J 


109  GEOLOGY. 

rocks  are  usually  associated  with  secondary  and  tertiary 
strata,  or  as  volcanic  products  are  mingled  up  with  the 
superficial  accumulations  now  in  progress ;  but  the  student 
is  not  on  this  account  to  suppose  that  granite  may  not  also 
be  found  in  conjunction  with  secondary  or  tertiary  strata. 

1 37.  The  geographical  distribution  of  granitic  rocks  is 
very  general ;  they  form  many  of  the  most  extensive  moun- 
tain ranges  in  the  world.     The  Grampians  in  Scotland,  the 
Cumberland  and  Cornwall  hills  in  England,  the  Wicklow 
mountains  in  Ireland,  the  Alps  in  Switzerland,  the  Pyrenees 
in  Spain,  the  Dofrafelds  in  Norway,  the   Abyssinian  and 
other  A'rican  ranges,  and  the  Andes  in  South  America, 
are  all  more  or  less  composed  of  rocks  partaking  of  a  gra- 
nitic character. 

138.  The  physical  geography  of  a  granitic  district  is  by 
no  means  remarkable  for  its  fine  scenery.    Where  the  rock 
is  soft,  the  hills  have  a  heavy  rounded  appearance,  and  are 
only  peaked  and  irregular  in  outline  where  it  is  hard,  and 
flanked  by  stratified  rocks.     Forming,  in  general,  very  lofty 
hills  and  elevated  table-lands,  granitic  districts  present  a 
bleak  and  barren  landscape,  which  is  rendered  still  more  so 
by  the  snow-clad  peaks  of  the  loftier  mountains. 

13i).  The  economical  uses  to  which  granitic  rocks  arid 
their  products  are  applied  are  by  no  means  unimportant. 
Compact  granite,  from  its  extreme  hardness,  is  largely 
etnployed  in  the  construction  of  docks,  lighthouses,  foun- 
dations, bridges,  and  other  structures  where  durability  is 
the  object  in  view.  Waterloo  Bridge  in  London,  the  Liver- 
pool and  other  English  docks,  are  built  of  Aberdeen  gra- 
nite. It  is  the  ordinary  building  stone  in  the  city  of 
Aberdeen.  The  pyramids,  Pompey's  pillar,  and  other 
ancient  Egyptian  structures,  are  composed  of  it,  as  are  also 
many  monumental  erections  in  our  own  country.  Within 
these  few  years,  the  red  granite  of  Peterhead,  in  Scotland, 
has  been  brought  into  use  as  an  ornamental  stone ;  and 
machinery  has  been  erected  to  polish  it  like  marble,  to 


398.  What  of  the  localities  of  granite  T 

399.  What  of  its  physical  geography  ? 

400.  What  of  its  economical  uses  7 


GNEISS    AND    MICA    SCHIST    SYSTEMS.  101 

which  many  prefer  it  for  chimney  slabs,  vases,  pedestals, 
&c.  Mica  and  talc  are  sometimes  found  in  crystals  more 
than  a  foot  square;  when  of  this  size,  they  are  split  up  into 
thin  plates,  and,  from  their  transparency,  used  in  some 
countries  as  a  substitute  for  glass.  Talc,  by  the  Russians, 
is  thought  preferable  to  glass  for  ship  light,  as  it  is  not  apt 
to  be  broken  by  the  firing  of  cannon ;  it  also  stands  a 
higher  degree  of  heat  than  glass  without  splintering.  Some 
varieties  of  felspathic  and  talcose  granites  are  easily  decom- 
posed by  exposure  to  the  atmosphere,  and  in  this  state  pro- 
duce a  fine  impalpable  powder  of  silica  and  clay,  of  great 
use  in  the  manufacture  of  porcelain,  Mosaic  tesserae,  but- 
tons, and  artificial  gems.  The  clay  from  decomposed  fel- 
spar is  known  in  China  by  the  name  of  kaolin,  and  is  used 
by  that  nation  in  the  manufacture  of  their  finest  china. 
According  to  Dr.  Boase,  upwards  of  12,000  tons  of  decom- 
posed felspar  (Cornith  clay)  are  annually  exported  from 
Cornwall  to  the  English  potteries. 

EXPLANATORY  NOTE. 

GRANITIC  GROUP. — To  the  many  varieties  of  this  group  Mr.  Lyell 
applies  the  term  hypogene  rocks  (Or.,  hypo,  under,  and  ginomai,  I  am 
formed) ;  that  is,  nether,  or  under-formed  rocks.  This  term  he  em- 
ploys to  avoid  any  theory  as  to  the  origin  of  granite  ;  but  it  has  not 
been  generally  adopted,  the  prevalent  belief  being,  as  mentioned  above, 
that  granite  is  of  igneous  origin  ;  that  it  has  resulted  from  the  gradual 
cooling  down  of  the  globe  while  in  an  incandescent  state  ;  and  that  it 
therefore  forms  a  basis  for  all  the  stratified  systems. 

GNEISS  AND  MICA  SCHIST  SYSTEMS. 

140.  Before  describing  the  primary  rocks,  it  is  necessary 
to  advert  to  a  general  fact,  applicable  to  the  character  of  all 
stratified  formations.  Silir.eoita,  argilfacfons,  calcareous,  and 
carboniferous  compounds,  may  be  said  to  constitute  the 
solid  crust  of  the  globe ;  and  these  compounds  differ  in 
their  appearance  and  mode  of  aggregation  according  to  the 

401.  What  of  mica  and  talc  ? 

402.  What  species  are  used  for  manufactures  T 

403.  What  two  systems  are  next  considered  T 

404.  What  four  compound*  are  said  to  form  the  crust  of  the  globe  I 


132  GEOLOGY. 

order  of  their  occurrence.  For  instance,  the  siliceous 
rocks  of  the  primary  strata  are  compact  and  crystalline;  in 
the  secondary  they  are  less  compact,  lose  their  crystalline 
appearance,  and  become  sandstones  of  various  degrees  of 
fineness ;  in  the  tertiary  they  are  often  so  soft  in  their  tex- 
ture as  to  be  called  sands:  while  in  the  superficial  they  are 
merely  loose  accumulations  of  sand  and  gravel.  So  it  is 
with  the  argillaceous  rocks — from  the  compact  and  glisten- 
ing clay-slates  of  the  primary,  through  the  slaty  shales  of 
the  secondary,  and  the  laminated  clays  of  the  tertiary  rocks, 
up  to  the  soft  plastic  clays  of  our  alluvial  valleys.  As  with 
the  siliceous  and  argillaceous,  so  with  calcareous  and  car- 
boniferous ;  hence  a  table  may  be  formed  exhibiting  these 
gradations : — 

Siliceous.  Argillaceous.  Calcareous.  Carboniferous. 

Sand,  Alluvial  Clay,  Marl,  Peat, 

Sandstone,  Laminated  Clay,  Chalk,  Lignite, 

Grauwacke,  Slaty  Shale,  Limestone,  Brown  Coal, 

Quartz  Rock.  Clay-Slate.  Crystalline  Marble.  Common  Coal. 

Thus,  as  we  descend  into  the  crust,  the  mineral  ingredients 
of  the  stratified  rocks  assume  different  degrees  of  aggrega- 
tion, gradually  becoming  harder  and  more  compact,  till 
ultimately  they  present  a  crystalline  texture  scarcely  dis- 
tinguishable from  the  granitic  basis. 

141.  The  composition  of  the.  primary  strata,  like  that  of 
the  granite  on  which  they  rest,  is  often  modified  by  the  pre- 
sence of  peculiar  minerals;  though  felspar,  quartz,  mica, 
talc,  hornblende,  and  chlorite,  constitute  the  greater  portion 
of  their  mass.  Gneiss,  or  the  oldest  system  of  stratified 
rocks,  differs  little  from  true  granite  in  its  mineral  compo- 
sition, except  in  as  far  as  regards  the  aggregation  of  the 
simple  minerals.  In  granite,  the  crystals  of  felspar,  quartz, 
mica,  and  hornblende,  are  entire  and  distinct;  in  gneiss, 
their  angles  and  frees  are  broken  and  water-worn.  In 
granite,  there  are  no  traces  of  a  laminated  or  stratified 
structure ;  in  gneiss,  this  structure  is  evident,  even  where 

405.  Describe  the  varieties  of  each  according  to  the  table. 

406.  How  do  they  vary  as  we  descend  into  the  crust? 

407.  What  minerals  constitute  the  chief  portion  of  primary  strata  7 

408.  Wherein  does  gneiss  ditfer  from  granite  ? 


GNEISS    AND    MICA    SCHIST    SYSTEMS.  133 

the  strata  are  most  indurated  and  contorted.  All  this  attests 
the  aqueous  origin  of  gneiss  —  that  it  must  have  been  de- 
posited in  water,  and  that  it  is  composed  of  the  disintegrated 
minerals  of  unstratified  granite. 

14*2.  The  stratified  structure  which  is  sometimes  confused 
and  indistinct  in  gneisst  is  much  more  apparent  and  regular 
in  mica  schist  The  particles  of  the  latter  are  more  water- 
worn,  and  the  abundance  of  fragmented  mica  gives  its  lami- 
nation a  degree  of  parallelism  not  to  be  found  in  the  former. 
Both,  however,  are  frequently  seen  passing  into  each  other, 
thus  rendering  it  difficult  to  distinguish  where  the  one  sys- 
tem ends  and  the  other  begins.  Passing  over  these  dubious 
strata,  the  mica  schist  system  is  composed  of  alternations  of 
mica  schist,  talcose  schist,  chlorite  schist,  hornblende  schist, 
quartz  rock,  primitive  or  crystalline  limestone,  with  occa- 
sional beds  of  clay-slate  in  the  upper  part  of  the  system. 
Independently  of  their  stratification,  the  mica  schist  rocks 
distinctly  indicate,  by  their  texture,  that  they  have  been 
formed  by  the  action  of  water.  The  particles  of  which 
they  are  composed  are  more  broken  and  rounded  than  those 
of  gneiss  —  a  circumstance  arising  from  the  fact,  that  they 
were  partly  derived  from  granite  and  partly  from  gneiss, 
which  must  thus  have  undergone  a  double  process  of  attri- 
tion. The  following  engravings  are  intended  to  represent 
the  external  appearance  of  granite,  gneiss,  and  mica  schist 
—  the  first  composed  of  distinct  crystals,  and  showing  no 
traces  of  lamination  ;  the  second  irregularly  laminated  ;  and 
the  third  finely  and  regularly  laminated. 


Granite.  Gneiss.  Mica  Schist. 

143.   Gneiss  and  mica  schist  differ  little  from  granite, 

409.  Whit  origin  is  hence  ascribed  to  gneiss  1 

410  What  of  mica  schist? 

41  1  Of  what  minerals  is  the  mica  schist  system  comoosed  1 

412  Point  out  the  distinctions  of  the  diagrams. 


1 34  GEOLOGY. 

and  still  less  from  one  another,  in  their  mineral  composi- 
tion ;  showing  clearly  that  it  is  chiefly  in  the  degree  of 
attrition  which  the  original  minerals  have  undergone,  that 
their  external  differences  consist: — 

GRANITE — of  felspar,  quartz,  and  mica  ;  felspar,  quartz,  hornblende  ; 
felspar  and  hornblende  ;  or  it  may  be  of  various  combinations  of  these 
simple  minerals. 

GNEISS — of  felspar,  quartz,  and  mica;  occasionally  with  hornblende 
and  garnets  in  it. 

MICA  SCHIST — of  mica  and  quartz,  with  hornblende  and  garnets  con- 
tained in  it. 

TALCOSE  SCHIST — of  talc  and  quartz,  and  differs  only  in  this  respect 
from  mica  schist. 

CHLORITE  SCHIST — of  chlorite  and  quartz. 

HORNBLENDE  SCHIST — of  quartz  and  hornblende,  occasionally  with 
actynolite. 

QUARTZ  ROCK  generally  contains  hornblende  or  mica  irregularly  im- 
bedded in  it. 

The  particles  of  the  primary  strata  are  indefinite  both  as  to 
srze  and  arrangement — some  are  fine  and  close-grained, 
others  are  conglomerate  and  coarse;  but  all  bear  evident 
trace.-  of  t'leir  aqueous  origin. 

144.  There  is  nothing  like  a  regular  order  of  succession 
among  the  primary  strata.  It  may  be  stated  generally,  how- 
ever, that  gneiss  underlies  the  mica  schist ;  that  mica  and 
other  crystalline  schists  are  the  lowest  in  the  system  ;  and 
that  quartz  rock,  primitive  limestone,  and  clay  schist,  make 
their  appearance  towards  the  upper  part  of  the  series. 
Stratification  is  sometimes  obscure,  and  not  very  persistent  ; 
that  is,  any  one  stratum  is  not  ibund  stretching  over  a  great 
extent  of  country,  as  is  the  case  with  the  secondary  rocks. 
A  seam  of  coal  will  often  be  found  stretching  over  ten  or 
twelve  miles  of  country,  without  much  difference  either  in 
quality  or  thickness;  but  in  the  primary  systems,  the  strata 
thicken,  thin  out,  and  disappear  in  a  very  capricious  man- 
ner. In  absence  of  any  thing  like  a  characteristic  section, 

413.  What  is  argued  from  the  slight  differences  in  their  mineral  com- 

position ? 

414.  Define  each  of  the  terms  by  their  composition. 

415.  What  of  the  particles  of  the  primary  strata  7 

416.  What  of  the  order  of  succession  in'the  primary  strata  T 

417.  How  is  thfiir  stratification  1 


GNEISS    AND    MICA    SCHIST    SYSTEMS.  105 

the  following  rocks  may  be  mentioned  as  constituting  the 
great  bulk  of  the  primary  formation : — Gneiss,  mica  schist, 
talc  schist,  chlorite  schist,  shorlaceous  schist,  stea  schist, 
hornblende  schist,  actynolite  schist,  quartz  rock,  crystalline 
limestone,  hornstone,  and  protogine.  Most  of  these  rocks 
pass  insensibly  into  each  other,  and  thus  many  compounds 
are  formed  of  which  the  student  can  only  obtain  a  know- 
ledge by  the  study  of  actual  specimens. 

145.  No  organic  remains  have  yei  been  discovered  in  the 
gneiss  or  mica  schist  systems ;  and  if  life,  either  in  a  vege- 
table or  animal  form,  existed  at  the  time  these  rocks  were 
deposited,  it  must  have  been  exceedingly  rare,  and  confined 
to  a  few  limited  points  on  the  earth's  surface.  (See  note, 
p.  108.) 

14(3.  As  to  the  origin  of  the  gneiss  and  mica  schist  sys- 
tems, it  is  abundantly  evident  that  the  materials  of  which 
they  are  composed  were  derived  from  the  underlying  gra- 
nite. It  has  been  stated  that  this  rock  forms  a  solid  and 
irregular  basis,  on  which  all  the  sedimentary  strata  rest; 
and  if  this  be  true,  it  is  evident  that  its  surface  must  have 
been  partly  under  and  partly  above  water,  and  subject  to 
the  degrading  influence  of  atmospheric,  aqueous,  and  che- 
mical agencies.  Moreover,  if  the  granitic  crust  was  formed 
by  the  cooling  of  an  originally  fused  globe,  the  waters  rest- 
ing in  the  hollows  must  have  been  heated  to  a  high  degree, 
and  the  air  must  have  been  loaded  with  vapours.  All  this 
would  further  tend  to  hasten  the  degradation  of  the  granite; 
the  runnels  and  streams  would  carry  down  the  loose  parti- 
cles, laying  down  the  heavier  first,  and  carrying  out  the 
lighter  and  smaller  to  deeper  water.  In  process  of  time 
the  loose  matter  would  get  consolidated  by  the  pressure  of 
its  own  mass ;  the  high  temperature  then  pervading  the 
globe,  together  with  chemical  agency,  would  assist  in  pro- 
ducing the  crystalline  texture;  and  thus  a  variety  of  schis- 
tose rocks  might  be  formed  at  one  and  the  same  time. 

418.  \\  hat  roeks  form  the  great  bulk  of  the  primary  strata  ? 

419.  Are  they  distinct  or  do  they  blend  into  each  other  1 

420.  What  is  the  inference  from  the  absence  of  organic  remains  ? 

421.  Whence  were  the  materials  of  the  piimary  strata  derived,  and 

how  accounted  for  f 


106  GEOLOGY. 

That  a  high  temperature  'existed  during  the  formation  of 
the  primary  rocks,  we  have  ample  evidence,  not  only  in 
their  hard  and  crystalline  texture,  and  in  the  absence  of  all 
organic  remains,  but  in  the  occurrence  of  certain  minerals, 
such  as  garnet,  whose  presence  denotes  that  the  rocks  in 
which  it  is  found  have  experienced  a  degree  of  heat 
sufficiently  light  to  form  such  a  fusible  mineral,  but  not 
enough  to  melt  the  other  constituents  of  which  they  are 
composed. 

147.  The  igneous  rocks  associated  with  the  gneiss  and 
mica  schist  systems  are,  as  may  be  anticipated,  the  granitic 
on  which  they  rest,  and  from  which  their  materials  have 
been  directly  derived.     Sometimes  the  granite  is  in  imme- 
diate contact  with  the  gneiss,  so  much  so,  as  to  render  it 
matter  of  difficulty  to  say  where  the  one  ends  and  the  other 
begins ;  at  other  times  it  touches  the  mica  schist,  or,  it  may 
be,  passes  through  both  in  the  form  of  dykes  and  veins. 
Later  igneous  rocks,  such  as  porphyry,  greenstone,  and  ser- 
pentine, are  frequently  found    traversing  the  gneiss  and 
mica  schist  in  dykes  and  protruding  masses;   and  occa- 
sionally, still   more  recent  effusions  of  trap  are  found  pass- 
ing through  the  primary  strata,  with  their  associated  dykes 
and  veins  of  granite.     Metalliferous  veins  are  not  of  fre- 
quent occurrence  in  the  primary  strata  of  the  British  isles, 
though  they  are  found   in  those  of  central  and  northern 
Europe.      Thermal    springs   are   perhaps  still   more   rare, 
though  abundant  enough  in  the  gneiss  and  mica  schists  of 
other  countries. 

148.  The  extent  of  country  occupied  by  the  primary  strata 
is  very  great,  although  as  yet  but  imperfectly  ascertained. 
They  occur  abundantly  in  the  Highlands  and  islands  of 
Scotland,  in  the  north  of  Ireland,  along  the  flanks  of  the 
Pyrenees,  the  Alps,  the  great  mountain  chains  of  northern 
Europe,  in  Asia,  in  Ceylon,  in  Africa,  and  in  America, 
particularly  in  the  Brazils  and  the  United  States. 

422.  What  is  inferred  from  the  occurrence  of  garnet? 

423.  What  igneous  rocks  are  found   in  the  gneiss  and  mica  schist 

systems  ? 

424.  What  of  metals  and  thermal  springs  ? 

425.  To  v.<ia    extent  are  the  primary  strata  ascertained? 


GNEISS  AND  MICA  SCHIST  SYSTEMS.  107 

140.  The  physical  aspect  of  primitive  districts  is  bold, 
rugged,  and  unfertile.  Thrown  into  lofty  mountains  by 
the  granite,  and  into  abrupt  and  vertical  positions,  it  is 
chiefly  among  gneiss  and  mica  schist  that  those  deep  glens 
and  abrupt  precipices  occur  which  give  the  well-known 
picturesque  effect  to  Highland  scenery.  The  student  will 
readily  perceive  how  this  effect  is  produced,  when  he  con- 
siders the  hardness  of  the  rocks,  and  the  highly  vertical 
and  contorted  positions  into  which  they  are  thrown  ;  where- 
as in  secondary  formations,  the  position  is  in  general  flatter, 
and  the  strata  so  soft,  that  they  cannot  present  the  same 
rugged  and  abrupt  appearance. 

150.  The  minerals  of  commerce  derived  from  these  systems 
are  by  no  means  numerous.     Several  of  the  metallic  ores, 
such  as  tin  and  copper,  occur  in  veins  traversing  these 
strata.     The  limestones,  from  their  highly  crystalline  tex- 
ture, in  general  produce  valuable  marbles  ;  but  none  of  the 
other  rocks  are  of  use  for  architectural  purposes.    Potstone, 
or  the  lapis  ollaris  of  the  ancients,  of  which  very  pretty  jars 
and  vases  are  manufactured,  is  found  in  stea  schist.     Ami- 
anthus, or  flexible  asbestus,  occurs  among  the  mica  schisis, 
and  is  sometimes  used  in  the  manufacture  of  fabrics  which 
are  indestructible  by  fire.    The  garnet  is  a  well-known  pre- 
cious stone ;  and  many  of  the  most  valuable  are  found  in 
the  rocks  of  this  system. 

151.  It  may  be  stated  generally  ofgnriss  and  mica  schistt 
that  they  are  the  oldest  sedimentary  rocks,  and  rest  upon 
masses  which  owe  their  origin  to  heat;  that  they  are  totally 
different  from  other  stratified  rocks,  inasmuch  as  their  par- 
ticles have  not  undergone  so  much  attrition,  and  likewise 
as  they  have  been  subjected  to  a  higher  degree  of  heat ; 
that  they  are  destitute  of  organic  remains,  arid  therefore 
afford  no  evidence  of  habitable  dry  land ;   and  lastly,  that 
they  are  spread  over  so  great  an  extent,  as  to  be  considered 
almost  universal. 


426.  What  of  the  physical  aspect  and  peculiarities  of  these  primitive 

districts  ? 

427.  What  of  the  minerals  of  commerce  in  these  systems? 

428.  Describe  their  jreneral  characteristics. 


103  GEOLOGY. 


EXPLANATORY    NOTE. 

SILICEOUS  (Lat.,  silex,  flint) — all  rocks  having  a  flinty  texture  are  said 
to  be  siliceous.  Quartz  is  the  purest  form  in  which  silex  occurs.  When 
grains  of  quartz  are  loosely  aggregated,  as  in  some  sandstones,  the 
locks  are  said  to  be  quart zose,  or  gritty. 

ARGILLACEOUS  (Lat.,  argilla,  clay) — rocks  composed  of  clay,  or  hav- 
ing a  considerable  portion  of  clay  in  their  composition,  are  said  to  be 
argillaceous. 

CALCAREOUS  (Lat.,  calx,  lime) — composed  of,  or  containing  a  con- 
siderable portion  of  lime. 

CARBOMFEROUS  (Lat.,  carbo,  coal,  or  charcoal) — rocks  containing 
conl,  or  associated  with  coal,  are  said  to  be  carboniferous.  Carbon- 
aceous is  applied  when  traces  of  carbon  appear  intermingled  with  their 
texture. 

SCHIST  (Gr.,  schisma,  a  splitting  or  division) — applied  to  rocks  easily 
split  up  into  slaty-like  plates  or  divisions,  as  mica  schist. 

GNEISS  AND  MICA  SCHIST. —  It  has  been  already  stated,  that  to  these 
systems  Mr.  Lyell  applies  the  term  met amor phi c,  meaning  thereby  that 
they  have  undergone  a  metamorphosis,  or  change,  in  their  sedimentary 
character,  so  as  frequently  to  be  mistaken  for  true  igneous  or  granitic 
rocks.  According  to  this  opinion,  gneiss  and  mica  schist  may  have 
contained  organic  remains,  the  traces  of  which  havo  since  been  obli- 
terated by  heat ;  even  granite  itself  may  be  a  highly  metamorphic 
rock — in  other  words,  that  it  may  be  altered  or  metamorphosed  sedi- 
mentary strata.  By  this  theory  all  stratified  systems  may  in  time  become 
metamorphic,  so  that  geology  can  never  hope  to  arrive  at  any  thing 
like  a  continuous  history  of  the  globe  from  its  origin  upwards — the 
older  strata  and  their  remains  being  thus  successively  obliterated. 
This  theory,  however,  has  not  been  generally  adopted,  and,  from  the 
plain  evidences  which  most  strata  afford  of  their  formation,  it  is  not 
likely  to  be  so. 

CLAY-SLATE,  GRAUWACKE,  AND  SILURIAN  SYSTEMS. 

152.  It  has  been  stated  that  the  four  great  types  of  all 
stratified  rocks  are  siliceous,  argillaceous,  calcareous,  and 
carboniferous ;  and  that,  in  general,  each  system  is  charac- 
terized by  some  prevailing  type.  The  gneiss  and  mica 
schists  have  been  described  as  eminently  siliceous:  we  shall 
now  learn  that  in  the  clay-slate,  grauwacke,  and  silurian 
systems,  argillaceous  compounds  prevail — almost  wholly  so 
in  the  first  system,  mingled  with  arenaceous  strata  in  the 

429.  Define  the  several  terms  of  the  note. 

430.  Why  does  Mr.  Lyell  use  the  term  metamorphic  ? 

431.  What  systems  are  next  considered  ? 

432.  To  which  type  of  stratified  rocks  do  these  belong  7 


CLAY-SLATE,  GRALWACKE,  AND  SILURIAN  SYSTEMS.     l'J3 

second,  and  with  calcareous  and  arenaceous  beds  in  the 
third. 

L>3.  The  clay-slate  system  presents  a  vast  thickness  of 
fine-grained  fissile  argillaceous  rock,  of  considerable  hard- 
ness,  varying  in  colour,  and  of  glistening  aspect.  The 
prevalent  colours  of  sjate  are  black,  green,  bluish,  purplish, 
and  mottled;  some  varieties  being  hard  and  splintery, 
others  soft  and  perishable.  The  character  of  any  particu- 
lar slate  is,  however,  very  persistent;  the  accidental  or 
imbedded  minerals  are  few — these  being  chiefly  cubic-iron 
pyrites,  and  crystals  of  chiastolite  and  hornblende. 

154.  The,  composition  of  the  grauwacke,  is  much  more 
varied  and  irregular.    As  sandstone  may  be  said  to  be  con- 
solidated sand,  and  conglomerate  consolidated  gravel,  so 
may  grauwacke  be  defined  to  be  an  aggregate  of  clay,  grains 
of  quartz,  felspar,  and  mica,  with  fragments  of  jasper  and 
other  minerals.      The  cementing  material  is  clay,  which 
often  constitutes  the  greater  portion  of  the  rock,  and  in 
such  cases  the  texture  differs  little  from  that  of  clay-slate; 
but  in  many  strata  fragmentary  ingredients  prevail,  so  that 
the  texture  varies  in  fineness  from  that  of  a  coarse  slate  to 
a  conglomerate  of  pebbles  more  than  an  inch  in  diameter. 
Like  clay-slate,  grauwacke  presents  various  degrees  of  hard- 
ness, though,  generally  speaking,  it  may  be  described  as  a 
highly  indurated  conglomerate — indicating  most  clearly  its 
origin  from  the  waste  of  earlier  siliceous  and  argillaceous 
formations.      Associated  with  the  slates  and   grauwackes 
are  occasional  beds  of  concretionary  limestone,  which  par- 
take of  the  argillaceous  character  of  the  rocks  with  which 
they  are  associated. 

155.  In  the  silurian  system,  limestones  occur  more  fre- 
quently, so  that  the  calcareous  type,  or,  at  all  events,  an 
intimate    blending   of  argillaceous   and   calcareous   com- 
pounds, may  be  said  to  prevail.     Until  a  recent  period,  this 
system  was  considered    as  a  portion  of  the    grauwacke 
group,  and  as  marking  its  passage  into  the  gray  micaceous 

433.  What  of  the  varieties  and  composition  of  the  clay  slate  ? 
4J4.  Ho'.v  does  grauwacke  diler  from  this  1 

435.  What  of  its  composition  and  varieties? 

436.  What  is  peculiar  in  the  silurian  system  ? 


1 1 0  GEOLOGY. 

beds  of  the  old  red  sandstone.  Merely  looking  at  cabinet 
specimens,  it  would  be  impossible  to  distinguish  between 
many  of  the  giauwacke  and  silurian  rocks,  but  taking  them 
in  the  mass  they  are  readily  distinguishable.  In  the  first 
place,  their  sedimentary  character  is  very  marked;  they 
present  more  rapid  alternations  from  one  kind  of  strata  to 
another;  they  have  undergone  fewer* changes  by  heat;  and 
are  generally  looser  and  more  earthy  in  their  texture.  The 
limestones  are  less  crystalline  than  those  of  the  early  grau- 
wackes;  the  arenaceous  beds  are  also  less  siliceous,  and 
more  closely  resemble  ordinary  sandstones,  while  the  abun- 
dance of  organic  remains  justifies  their  arrangement  into  a 
separate  system. 

156.  From  this  description  of  these  systems,  it  will  be 
seen  that  their  main  type  is  argillaceous;  eminently  so  in 
the  clay-slates;    abundantly   enough    in    the    grauwackes, 
which  pass,  in  texture,  from  slate  to  a  coarse  quartzose 
conglomerate  ;  and  perceptibly  in  the  silurian  limestones, 
which  are  all  of  a  dark  argillaceous  character.     It  is  also 
worthy  of  notice,  that  the  crystalline  aspect  which  charac- 
terized the  Primary  Rocks  disappears  with  the  clay-slates, 
and  gradually  passes  into  an  earthy  or  arenaceous  texture 
in  the  grauwacke  and  silurian.     It  is  true  that  some  of  the 
lower  slates  have  a  glistening  semi-crystalline  appearance; 
but,  taken,  in  the  mass,  arid  in  conjunction  with  the  grau- 
wacke and  silurian  rocks,  the  whole  materials  of  these  sys- 
tems are  more  loosely  arranged,  and  more  decidedly  sedi- 
mentary, than    the   gneiss  and  mica  schists.     The  term 
Transition  has  been  applied  to  the  series,  as  not  only  indi- 
cating a  change  in  the  causes  of  formation,  but  implying 
that  the  world  was  then  passing  from  an  uninhabitable  to 
an  inhabitable  state. 

157.  The  stratified  structure  is  abundantly  obvious  in 
the  rocks  of  the  transition  series.    The  occurrence  of  inter- 
stratified  limestones,  and  the  bands  of  different  colour  and 
hardness  in  the  slates,  all  point  to  deposition  in  water; 

437.  Wherein  do  they  differ  from  grauwacke  ? 

438.  Of  what  type  are  these  three  systems  t 

439.  Why  is  the  term  transition  applied  to  this  series  1 

440.  What  proves  their  aqueous  origin  1 


CLAY-SLATE,  GRAUWACKE,  AND  SILURIAN  SYSTEMS.      I  I  I 

while  the  succession  of  fine  and  coarse-grained  grauwackes, 
of  siiurian  limestones  and  shales,  is  as  decisive  of  stratifi- 
cation as  alternations  of  sandstone,  shale,  and  coal.  From 
this  statement,  the  student  must  not,  however,  expect  to 
find  the  sedimentary  structure  very  distinctly  marked  in  the 
chy-slatcs;  it  is  only  in  the  grauwacke  and  siiurian  that 
this  is  decided.  Lamination  may  be  said  to  prevail  in  the 
rocks  of  fine  texture,  and  stratification  in  those  of  an  are- 
naceous or  calcareous  character.  The  laminated  structure 
of  grauwacke  is,  however,  of  a  different  character  from 
lamination  in  clay-slate;  in  the  former  it  is  the  result  of 
deposition,  in  the  latter  it  is  the  effect  of  a  subsequent 
change  which  the  rock  has  undergone,  called  cleavage. 

15K  Cltavage  differs  from  ordinary  lamination  in  this 
respect,  that  it  causes  clay-slate  to  split  up  into  thin  plates 
at  right  angles,  or  nearly  so,  to  fhe  bed  of  stratification. 
while  lamination  simply  implies  that  any  stratum  can  be 
split  up  into  a  number  of  thinner  layers  or  laminae.  Cleav- 
age occurs  in  several  varieties  of  rock,  but  it  is  most  regular 
and  distinct  in  clay-slate ;  and  it  is  owing  to  this  structure 
that  the  rock  has  the  property  of  being  split  up  into  thin 
divisions  for  roofing  and  other  purposes.  The  appearance 
which  cleavage  presents  in  the  mass  is  represented  beneath, 
by  the  nearly  perpendicular  lines  cutting  those  of  stratifica- 


Section  eihibiting  lines  of  Cleavage. 

tion  at  a  high  angle.  How  cleavage  has  been  produced,  is 
still  an  undecided  problem  among  geologists;  though  it 
may  be  stated  generally,  that  it  seems  to  have  taken  place 
long  after  the  deposition  of  the  strata  in  which  it  occurs,  and, 
like  crystallization,  to  owe  its  origin  to  the  influence  either 
of  heat  or  of  electricity,  or  perhaps  to  both.  (See  note.) 

441.  What  of  the  sedimentary  structure  7 

442.  What  of  lamination  and  cleavage? 

443.  Explain  the  diagram. 


GEOLOGY 


159.  The  succession  of  strata  in  the  clay-slate,  gran- 
wacke,  and  silurian  systems,  has  not  yet  been  very  clearly 
ascertained.  In  general  terms,  it  may  be  stated  that  the 
lower  slates  partake  of  a  micaceous  or  hornblendic  charac- 
ter ;  that  they  become  less  crystalline  as  we  ascend  in  the 
series,  and  are  succeeded  by  finely-laminated  grauwacke, 
with  interstratified  limestones.  In  the  grauwacke  there  is 
no  apparent  order  of  succession,  although,  in  most  locali- 
ties, limestones  and  argillaceous  beds  prevail  in  the  lower, 
and  grits  and  conglomerates  in  the  upper  portion  of  the 
system.  In  the  silurian,  order  is  still  less  obvious;  but,  on 
closer  study,  it  is  found  that  grits  and  grauwacke-looking 
rocks  prevail  in  the  lower  portion  of  the  system,  dark- 
coloured  shales  and  limestones  in  the  middle,  and  slaty  mi- 
caceous sandstones  in  the  upper.  The  following  detailed 
section  will  convey  to  the  student  a  more  correct  idea  of 
the  order  and  succession  among  these  systems : — 

1.  Slightly  micaceous  thin-bedded  sandstones. 

2.  Gray  and  blue  argillaceous  limestones. 

3.  Liver-coloured  shale,  with  concretions  of  earthy 

limestone. 

4.  Highly  concretionary  subcrystalline  blue  and  gray 

limestone. 

5.  Dark-gray  argillaceous    shale,  with    nodules   of 

earthy  limestone. 

6.  Thin-bedded  impure  limestone,  containing  shells, 

alternating  with  finely-laminated  micaceous 
sandstone  of  a  greenish  colour. 

7.  Sandstones,  grits,   and    limestones ;    arenaceous 

beds  prevailing. 

8.  Dark-coloured   flags,   chiefly   calcareous ;    sand- 

stones and  sandy  schists. 

9.  Grauwacke  slates   and  sandstones,  coarse  lime- 

stones, and  thick-bedded  grauwacke  rocks. 

10.  Dark    argillaceous    limestone,    with    shells    and 

corals. 

11.  Peculiar  slaty  and  flaggy  beds:  mottled  in  colour ; 

sometimes  coarse  and  conglomerate,  generally 
of  moderate  fineness,  alternating  with  coloured 
clayey  beds. 

12.  An  immense   thickness  of  clay-slate  of  various 

colours — blue,  black,  greenish,  purple,  or  mot- 
tled ;  of  fine  grain,  sometimes  compact,  some- 
times soft  and  useless. 


SILURIAN.  < 


GRAU- 
WACKE. 


CLAY-SLATE 


1 


444.  What  of  the  succession  of  strata  in  these  systems  T 

445.  Explain  the  tabular  arrangement. 


CLAY-SLATE,  GRAUWACKF,  AND  9U  t'RIAN  SYSTEMS.     113 

160.  The  organic  remains  of  these  systems  are  possessed 
of  more  than  ordinary  interest,  from  the  fact  of  their  being 
the  earliest  forms  of  life  with  which  we  are  acquainted.    In 
the  preceding  systems  we  have  no  traces  either  of  vegetable 
or  of  animal  existence :  life  begins  to  dawn  only  with  the 
development  of  the  clay-slate  group,  and  to  become  more 
abundant  as  the  deposition  of  the  grauwacke  and  silurian 
proceeds.     The  earliest  forms  of  vitality  are  not  plants, 
but  animals — animals  undoubtedly  low  in  the   scale  of 
organized  being,  but   still    perfect   animals,   as   perfectly 
adapted  to  the  condition  of  things  under  which  they  had  to 
live  as  those  now  existing.     They  are  wholly  marine;  and 
here  it  may  be  observed,  that  no  remains  of  terrestrial  ani- 
mals have  yet  been  discovered  by  geologists  earlier  than 
towards  the  close  of  the  Secondary  Formations.   In  the  clay- 
slate  and  grauwacke,  no  traces  of  vegetable  organism  have 
been  found,  and  only  about  thirty  species  of  corals  and 
shell-fish ;    in  the  silurian,  animal  remains  become  much 
more  abundant;  but  doubt  is  entertained  respecting  some 
fragments  of  sea-weeds  and  ferns  said  to  belong  to  this  for- 
mation.    Whether  the  remains  of  plants  and  animals  were 
entombed  in  these  earlier  formations,  and  have  since  been 
obliterated  by  the  agency  of  heat,  geological  science  has 
not  been  able  to  determine;  but  at  present,  we  are  war- 
ranted in  stating,  that  only  a  few  rare  corals  and  shells 
occur  in  the  clay-slate  system ;  a  greater  number  of  corals, 
shells,  and  Crustacea  in  the  grauwacke;  and  a  variety  of 
corals,  shells,  Crustacea,  fish  bones,  and  teeth,  in  the  silu- 
rian.   So  far  as  they  have  been  examined,  all  these  remains 
belong  to  species  long  since  extinct ;  indeed,  are  distinct 
from  those  which  occur  in  the  Secondary  Strata,  and  bear 
only  a  generic  resemblance  (often  a  faint  one)  to  existing 
races. 

161.  From  the  scantiness  and  peculiarity  of  organic  life, 
it  is  difficult  to  arrive  at  any  conclusion  as  to  the  condition 

446    What  of  the  organic  remains  found  here  ? 

447.  What  kind  of  animals  exclusively? 

44S.  Where  are  terrestrial  animals  to  be  sought  for  t 

449.  Are  the  animals  found  of  any  existing  species  T 

4oO.  What  is  argued  from  their  scantiness  and  peculiarities  t 


114 


GEOLOGY. 


of  the  world  at  this  early  period.  The  existence  of  shell- 
fish would  seem  to  indicate  the  co-existence  of  marine  plants 
upon  which  they  fed;  and  though  we  are  aware  that  mol- 
luscous animals  might  prey  upon  each  other,  still,  the  pro- 
bability is,  that  marine  vegetation  was  to  some  extent  spread 
over  the  bottom  of  the  transition  seas.  The  preponderance 
of  coral-like  animals  points  to  a  warm  and  favourable  con- 
dition of  the  waters  for  their  development ;  and  it  may  be 
that  this  highly  heated  condition  entirely  prevented  the 
growth  of  terrestrial  plants,  and  rendered  even  those  of 
marine  growth  of  so  rare  occurrence.  Be  this  as  it  may, 
we  are  only  certain  of  several  species  of  Zoophytes,  Mol- 
lusca,  and  Crustacea  in  the  clay-slate  and'grauwacke  rocks 
— among  which  the  most  characteristic  are  those  exhibited 
in  the  following  group: — 


1.  Cyathophyllum  Cyathus  ;   2.  Heliopora  Porosa  ;  3.  Catenipora  La- 
byrinthica  ;  4.  Producta  ;  5.  Spy-ifera  ;  6.  Terebratula. 

162.  The  fossils  of  the  Silurian  system  are  much  more 
abundant ;  there  are  a  greater  number  of  species  belonging 
to  each  genus;  annulosa, Crustacea,  and  fishes,  are  decided; 
and,  according  to  many  geologists,  plants  allied  to  the  algae 

451.  What  inferences  seem  authorized  ? 

452.  Explain  the  diagrams. 

453.  What  of  the  fossils  of  the  silurian  system  T 

454.  What  classes  o*"  animals  are  found  here,  and  what  varieties  I 


CLAY-SLATE,  GRAUWACKE,  AND  SILURIAN  SYSTEMS.      115 

(sea-weeds),  the  equisetaceae  (horse-tails),  filices  (ferns),  and 
others,  make  their  appearance.  Passing  over  the  remains 
of  plants  and  true  vertebrated  fishes,  about  the  existence  of 
which  at  this  period  there  is  still  great  obscurity,  we  shall 
notice  some  of  the  ascertained  peculiarities  of  the  radiata, 
mollusca,  and  articulata  belonging  to  the  Transition  era. 

163.  The  waters  of  the  Silurian  period  seem  to  have 
been  crowded  in  some  localities  with  zoophytes  and  corals, 
for  certain  limestones  are  as  much  composed  of  their  re- 
mains as  a  coral  reef  is  of  recent  corals.  Among  the  radi- 
ata, the  crinoid  or  encrinitc  family  occur  for  the  first  time, 
these  differing  from  other  corals  (see  par.  309)  in  the  self- 
dependent  nature  of  their  structure,  their  fixed  articulated 
stalk,  and  floating  stomach  furnished  with  movable  rays  for 
the  seizure  and  retention  of  their  food.  The  shell-fish  also 
become  more  numerous  and  distinct  in  form ;  spirifcrce, 
terebratida,  and  products,  are  every,  where  abundant :  and 
chambered  shells,  like  the  existing  nautilus,  begin  to  people 
the  waters.  It  must  be  remarked,  however,  that  the  encri- 
nites  and  chambered  shells  of  this  early  period  are  not  so 
numerous,  so  gigantic,  or  so  perfect  in  their  forms,  as  those 
of  the  Secondary  Strata ;  it  is  in  the  mountain  limestone 
group  that  the  crinoidea  attain  their  meridian,  and  in  the 
lias  and  oolite  that  the  ammonites  and  nautili  are  most  fully 
developed.  Of  the  Crustacea  of  this  era,  the  most  interest- 
ing and  abundant  type  is  the  trilobite  (three-lobed),  of 
which  several  genera  and  many  species  have  been  de- 
scribed, and  to  which  scarcely  any  existing  creature  bears 
an  analogy.  The  trilobite  (see  7,  H,  9  in  the  following 
engraving)  was  a  true  crustacean,  covered  with  shelly 
piates,  terminating  variously  behind  in  a  flexible  extremity, 
and  furnished  with  a  head-piece  composed  of  larger  plates, 
and  fitted  with  eyes  of  a  very  complicated  structure.  It  is 
supposed  by  some  to  have  made  its  way  through  the  water 
by  means  of  soft  paddles,  which  have  not  been  preserved; 
and  by  others  merely  to  have  sculled  itself  forward  by  the 
aid  of  its  flexible  extremity.  Of  its  various  organs,  the 
most  interesting  is  the  eye,  of  which  several  specimens  have 

455.  What  wonderful  structure  .is  found  in  the  trilobite  ? 


116 


GEOLOGY. 


been  obtained  in  a  very  perfect  state.  This  organ,  accord- 
ing to  fossil  anatomists,  is  formed  of  4JO  spherical  lenses 
in  separate  compartments,  on  the  surface  of  a  cornea  pro- 
jecting conicaJly  upwards,  so  that  the  animal,  in  its  usual 
place  at  the  bottom  of  waters,  could  see  everything  around. 
As  there  are  two  eyes,  one  of  the  sides  of  each  would  have 
been  useless,  as  it  could  only  look  across  to  meet  the  vision 
of  the  other;  but  on  the  inner  sides  there  are  no  lenses, 
that  nothing  may,  in  accordance  with  a  principle  observable 
throughout  nature,  be  thrown  away.  It  is  found  that  in 
the  strolls,  a  surviving  kindred  genus,  the  eyes  are  con- 


l.Astrea;  2.  Turbinolia  Fungites  ;  3.  Terebratula  Risca;  4.  Lep- 
ta>.na  Lata  ;  5.  Actinocrinites  ;  6.  Euomphalus  Rugosus  ;  7.  Asaphus  de 
liuchii  ;  8.  Asaphus  Tuberculatus  ;  9.  Calymene  Biumenbachii  ;  9a.  Side 
view  of  Calymene  while  rolled  up. 


456.   What  of  the  serolis  ? 


CLAY-SLATE,  GRAUWACKE,  AND  SILURIAN  SYSTKMa.     11? 

structed  on  exactly  tlie  same  principle,  except  that  they  are 
not  so  high — a  necessary  difference,  as  the  back  of  the 
seroJis  is  lower,  and  presents  less  obstruction  to  the  crea- 
ture's vision.  This  little  organ  of  a  trivial  little  animal 
carries  to  living  man  the  certain  knowledge  that,  many  ages 
ago,  the  air  he  breathes,  and  the  light  by  which  he  sees, 
were  the  same  as  at  this  hour,  and  that  the  sea  must  have 
been  in  general  as  pure  as  it  is  now.  If  the  water  had  been 
constantly  turbid  or  chaotic,  a  creature  destined  to  live  at 
the  bottom  of  the  sea  would  have  had  no  use  for  such  deli- 
cate visual  organs.  "  With. regard  to  the  atmosphere,"  says 
Dr.  Buckland,  "  we  infer  that,  had  it  differed  materially 
from  its  actual  condition,  it  might  have  so  far  affected  the 
rays  of  light,  that  a  corresponding  difference  from  the  eyes 
of  existing  crustaceans  would  have  been  found  in  the  organs 
on  which  the  impressions  of  such  rays  were  then  received. 
Regarding  light  itself  also,  we  learn,  from  the  resemblance 
of  these  most  ancient  organizations  to  existing  eyes,  that 
the  mutual  relations  of  light  to  the  eye,  and  of  the  eye  to 
light,  were  the  same  at  the  time  when  crustaceans  endowed 
with  the  faculty  of  vision  were  placed  at  the  bottom  of  the 
primeval  seas,  as  at  the  present  moment." 

1()4.  The  animals  of  this  early  period,  like  those  now  ex- 
isting, were  partly  herbivorous  (living  on  plants),  and  partly 
carnivorous  (living  on  the  jitsh  of  others).  The  polypes 
and  crinoidea,  it  is  true,  merely  secreted  limy  matter  from 
the  waters  of  the  ocean  wherewith  to  build  their  calcaredus 
structures;  but  while  certain  tribes  of  shell-fish  were  living 
on  the  sea-weeds  which  flourished  along  the  shores,  other 
races  were  preying  upon  these,  or  upon  each  other.  Among 
the  vegetable  eaters  were  the  products,  terebratulae,  &c.; 
the  ammonites  and  trilobites  were  those  which  lived  upon 
others. 

16j>.  That  the.  transition  strata  hnve  been  derived  partly 
from  the  disintegrated  materials  of  the  gneiss  and  mica 

457.  What  does  this  structure  demonstrate  in  relation  to  the  ancient 

earth  ? 

458.  How  IB  this  argued  by  Dr.  Buckland  1 

4-59.  What  of  those  herbivorous  and  carnivorous  J 
460.  Whence  were  the  transition  strata  derived  f 
(5 

.* 


1 18  GEOLOGY, 

schists,  and  partly  from  the  granite,  is  abundantly  obvious 
In  the  gneiss  and  mica  schists,  the  primitive  crystals  of  the 
granite  in  many  instances  had  undergone  little  attrition, 
and  in  most  cases  only  sufficient  to  make  them  arrange 
themselves  in  a  flat  or  laminated  position.  In  the  transi- 
tion systems,  the  material  has  suffered  sometimes  both  a 
mechanical  and  chemical  change.  The  felspar  of  the  gra- 
nite and  primary  strata  presents  itself  in  the  clay-slate  as  a 
soft  argillaceous  sediment,  destitute  of  the  potash  and  soda 
which  entered  into  its  crystallized  condition.  The  quartz 
presents  itself  in  sandy  grains,  without  any  particular  form, 
sometimes  finely  pulverized,  at  other  times  coarse  and 
gritty.  The  mica  is  variously  disseminated,  scarcely  ap- 
pearing in  some  strata  of  the  grauwacke;  but  occurring  in 
others  of  the  silurian,  so  as  to  give  them  a  micaceous  and 
laminated  aspect.  All  this  implies  the  combined  agency 
of  air  and  water — the  atmosphere  to  assist  in  the  chemical 
decomposition  of  the  felspar,  water  to  transport  it  to  the 
sea  of  deposit.  The  fineness  and  thickness  of  the  clay-slate 
deposit  indicates  an  im.'nense  depth  of  still  water;  the 
sandy  and  conglomerate  beds  of  the  grauwacke  not  only 
the  action  of  rivers,  but  the  action  of  the  sea  upon  its  shores  ; 
while  the  calcareous  beds  of  the  silurian  implies  the  agency 
of  the  coral  animal,  precisely  similar  to  that  now  going  for- 
ward in  the  Pacific.  Here,  then,  we  have  a  condition  of 
the  world  with  hills  and  valleys,  rivers  and  seas — the  atmos- 
pheric agents  acting  upon  the  cliffs  and  precipices;  the 
aqueous  also  degrading  the  rocks,  transporting  the  material, 
and  depositing  it  along  the  shores  of  seas,  whose  waters 
gave  birth  to  corals,  shell-fish,  and  fishes.  Fine  clayey  silt 
formed  clay-slate;  sand  and  other  mud  slaty  sandstones; 
gravel  grauwacke  conglomerate;  and  coral  polypes  beds 
and  reefs  of  limestone.  We  have  no  evidence  of  terrestrial 
life ;  and  the  necessary  inference  is,  that  the  conditions  of 
the  world  did  not  then  permit  of  its  being  called  into  ex- 
istence. 

461.  How  is  the  agency  of  both  air  and  water  shown? 

462.  What  other  indications  are  furnished  by  these  systems  ? 

463.  What  peculiarities  of  the  ancient  earth  are  here  considered  as 

proved  1 


CLAY-SLATE,  GRAUWArKE,  AN l>  SILURIAN  SYSTEMS.      1  19 

106.  The  igneous  rocks  associated  with  the  transition 
scries  are  granite,  serpentine,  porphyry,  greenstone,  varieties 
of  trap,  and  mineral  veins.  Indeed  there  is  scarcely  a  de- 
velopment of  the  clay-slate  or  grauwacke  systems  without 
associated  granitic  rocks ;  and  the  greater  portion  of  the 
silurian  strata  are  thrown  into  inclined  and  contorted  posi- 
tions by  the  same  agency,  while  effusions  of  trap  make  their 
appearance  among  the  latter  strata.  Perhaps  the  most  ex- 
tensive and  gigantic  efforts  of  volcanic  power  were  exhib- 
ited at  the  close  of  this  period;  and  there  is  abundant 
proof  that  all  the  principal  mountain  chains  in  the  world 
were  then  upheaved  The  Grampian  and  Welch  ranges, 
the  Pyrenees,  Hartz  mountains,  Dofrafelds,  Uralian,  Him- 
inaleh,  Atlas  range,  Mountains  of  the  Moon,  and  other 
African  ridges,  the  Andes,  and  Alleghanies,  all  seem  to 
have  received  their  present  elevation  at  the  close  of  the 
transition  period.  From  this  fact,  the  student  will  more 
readily  perceive  how  the  primary  and  transition  strata 
should  be  thrown  into  highly  inclined  and  contorted  posi- 
tions;  how  they  should  be  traversed  by  so  many  dykes  and 
mineral  veins;  and  how  slaty  cleavage,  and  other  alterations 
by  heat,  should  have  taken  place. 

167.  The  extent  of  country  over  which   the  day-slate, 
grauwackf,  and  silurian  systems  fir"  spread,  must  be  suffi- 
ciently indicated  by  the  mention  oi  .he  principal  mountain 
ranges  in   the  world,  from  whose  sui  s  and  flanks  their 
strata  slope  away  for  many  leagues  on  either  side. 

168.  The  geographical  features  of  transition  districts 
are  bold  and  mountainous,  and  are  well  illustrated  by  the 
characteristic  scenery  of  Wales,  the  Cumberland  Lakes, 
and    the    Scottish  Highlands.      "  Supported    by  granite," 
says  Professor  Phillips,  "  and  mixed  with  igneous  masses, 
the  slaty  rocks  of  the  English  lakes  rise  to  more  than  3000 
feet  in   height,  and  present  a  variety  of  outline,  and  intri- 
cacy of  combination,  which,  in  connexion  with  clear  lakes 
and  considerable  waterfalls,  leave  to  Switzerland  little  supe- 


464.  What  igneous  rocks  are  found  in  the  transition  series  ? 

465.  What  characterized  the  transition  period  of  the  earth's  history  1 

466.  What  of  their  localities  and  physical  geography  7 


2  GfcOLOGY. 

riority."  This  grandeur,  intricacy,  and  variety  of  aspect 
can  be  readily  accounted  for,  when  we  consider  tiie  height 
to  which  these  strata  have  been  elevated,  the  vertical  posi- 
tions into  which  they  are  thrown,  and  the  irregularity  of 
their  composition,  which  allows  them  to  be  scooped  out 
and  worn  down  to  a  thousand  forms — here  craggy  and 
splintery,  there  sinking,  or  rather  cleft  into  fearful  gorges 
and  ravines. 

lf>9.  The  economic  uses  to  which  the  minerals  of  these 
systems  are  applied  are  numerous  and  important.  From 
the  clay-slate  are  derived  roofing-slate,  writing-slate,  and  a 
variety  of  slates  for  ornamental  and  other  purposes.  Flag- 
stones and  pavement  are  obtained  from  the  grauwacke  and 
silurian  beds,  and  several  ornamental  marbles  from  the 
limestone  of  the  same  systems.  But  the  mere  rock  min- 
erals ate  of  little  value  in  comparison  with  the  metfillic 
veins  found  in  these  strata.  Tin,  lead,  copper,  silver,  gold, 
and  other  metals,  are  found  abundantly  in  the  veins  which 
traverse  the  clay-slate;  indeed  they  form  in  Britain,  as  well 
as  in  other  countries,  the  principal  metalliferous  rocks, 
with  the  exception  of  the  lead  and  ironstone,  of  the  carbon- 
iferous system. 

EXPLANATORY  NOTE. 

GRAUWACKE — a  German  miner's  term,  signifying  gray  rock  ;  adopted 
in  geology  to  designate  the  grayish  slates  and  siliceous  conglomerates 
of  the  transition  strata.  English-geologists  have  conferred  upon  this 
group  the  name  of  Cambrian,  from  its  forming  a  large  portion  of  the 
surface  of  Cambria  or  Wales  ;  the  term  grauwacke  is  more  general  and 
descriptive. 

SILURIAN — a  term  invented  by  Mr.  Murchison  to  designate  those 
calcareous  and  argillaceous  beds  which  lie  between  the  grauwacke  and 
old  red  sandstone.  The  word  is  derived  from  Silures,  the  name  of  an 
ancient  tribe  who  inhabited  that  district  of  country  between  England 
and  Wales  where  these  rocks  are  very  clearly  developed. 

PYRITES — a  mineral  composed  of  sulphur  and  iron — sulphuret  of  iron. 
If  is  usually  of  a  brass-yellow  colour,  brilliant,  and  crystallized.  Those 
little  shining  crystals  so  abundant  in  some  kinds  of  roofing-slate  are 
cubic  pyrites.  The  name  is  derived  from  the  Greek,  pyr,  fire  ;  because 
the  mineral  occasionally  produces  spontaneous  combustion. 

LAMINATION  (Lat.,  lamina,  a  leaf  or  blad«) — applied  to  thin  layers 
or  leaf-like  divisions  of  rocks. 

ARENACEOUS  (Lat.,  arena,  sand) — sandy.     Rocks  chiefly  composed 

467.  What  are  the  economical  uses  of  these  minerals  T 

468.  Define  the  terms  found  in  the  note. 


OLD  RED  SANDSTONE  SYSTEM.  121 

of  sand  are  described  as  arenaceous.  The  principal  constituent  of  sand 
is  quartz  or  silex  ;  and  the  terms  siliceous,  quartzose,  and  arenaceous, 
are  applied  to  rocks  according  to  the  appearance  which  their  textures 

£  resent.     Thus,  highly  indurated  and  close-grained  sandstone  is  said  to 
e  siliceous  ;  if  the  particles  of  quartz  be  large  and  distinct,  quartzose ; 
and  if  moderately  fine,  and  rather  loose  in  texture,  arenaceous. 

GRITS— hard  sandstone,  in  which  the  grains  of  quartz  are  sharp  and 
angular,  are  technically  called  grits,  as  millstone-grit,  grindstone- 
grit,  &c. 

CLEAVAGE. — The  peculiarities  of  this  structure  have  given  rise  to 
many  speculations  and  experiments.  Mr.  R.  W.  Fox  submitted  a  mass 
of  moist  clay,  worked  up  with  acidulated  water,  to  a  weak  electric 
action  for  several  months  ;  and  it  was  found  at  the  end  of  that  time  to 
present  traces  of  cleavage,  the  laminae  being  at  right  angles  to  the  elec- 
tric forces.  Others  .ire  of  opinion  that  cleavage  is  superinduced  when 
considerable  chemical  action  takes  place  in  any  finely  pulverized  sub- 
stance as  clay — cleavage  being  thus  regarded  as  a  species  of  rude 
crystallization.  Another  class  of  theorists,  from  observing  that  slaty 
cleavage  occurs  among  the  shales  of  the  coal  measures,  when  these  are 
in  the  neighbourhood  of  igneous  rocks,  attribute  the  structure  to  heat. 
It  is  not  unlikely  that  all  these  causes  may  have  been  concerned  in 
producing  cleavage  ;  for,  when  better  understood,  it  is  more  than  pro- 
bable that  heat,  electricity,  and  chemical  action,  are  ouly  modifications 
of  one  universal  agency. 

OLD  RED  SANDSTONE  SYSTEM. 

170.  Until  a  comparatively  recent  period,  geologists  were 
accustomed  to  consider  gneiss,  mica  schist,  clay-slate,  and 
old  red  sandstone,  as  sufficiently  distinctive  of  all  the  strati- 
fied systems  which  lay  underneath  the  coal  measures.  We 
have  seen,  however,  that,  in  point  of  mineral  composition, 
as  well  as  in  organic  remains,  the  clay-slate  differs  essen- 
tially from  the  grauwacke;  and  that  grauwacke,  as  we 
ascend,  begins  to  lose  its  arenaceous  character,  and  to  be 
succeeded  by  a  series  of  argillaceous  and  calcareous  beds 
more  prolific  in  fossils,  and  in  the  mass  perceptibly  differ- 
ent. To  this  series  of  strata  Mr.  Murchison  applied  the 
term  Silurian  system — a  system  which  may  be  said  to  par- 
take of  the  character  of  the  grauwacke  beds  beneath,  as  it 
insensibly  passes  into  the  gray  micaceous  flagstones  of  the 
o!d  red  sandstone  above.  The  student  must  not,  however, 
suppose  that  all  these  systems  are  to  be  met  with  fully  de- 


469.  What  of  grits  and  cleavage  7 

170.  What  theory  is  broached  of  the  identity  of  heat,  electricity  and 
c!;pmicai  agency? 

47 1 .  What  of  the  old  red  sandstone  system  f 


122  GEOLOGY. 

veloped  in  every  country;  all  that  the  science  of  geology 
affirms  is,  that,  when  they  are  present,  the  above  is  their 
order  of  occurrence,  and  the  general  aspect  and  character 
they  assume.  Sometimes,  indeed,  the  clay-slate  is  repre- 
sented by  a  few  indistinct  argillaceous  beds;  and  in  many 
places  it  is  difficult  to  discover  anything  like  a  well-defined 
series  of  strata  corresponding  to  the  silurian  rocks  of  Mr. 
Murchison;  but,  generally  speaking,  there  is  always  some 
shade  of  distinction,  either  in  mineral  or  fossil  character, 
which  enables  us  to  trace  the  gradation  of  these  successive 
systems.  VV  hatever  difficulty  may  be  experienced  in  ascer- 
taining (he  presence  and  limits  of  the  grauwacke  and  silu- 
rian systems,  there  is  seldom  any  doubt  as  to  the  old  red 
sandstone,  which,  in  the  British  islands,  is  one  of  the  most 
clearly  developed  of  rock  formations. 

171.  T/ie  composition  of  the  old  red  sandstone,  as  indi- 
cated by  the  name,  is  chiefly  arenaceous,  presenting  a  suc- 
cession of  sandstones  alternating  with  subordinate  layers  of 
sandy  shale.  The  sandstones  pass,  in  fineness,  from  close- 
grained  fissile  flags  to  thick  beds  of  conglomerate,  the  latter 
being  composed  of  pebbles  from  the  size  of  a  hazel-nut  to 
ihat  of  a  man's  head.  The  whole  system  is  tinged  with 
the  peroxide  of  iron,  the  colours  ranging  from  a  dark  rusty 
gray  to  brick-red,  and  from  a  mottled  purple  and  fawn  shade 
to  axiream-yellow.  The  mottled  aspect  is  principally  found 
in  the  shales  which,  from  their  sandy  character,  may  be 
regarded  as  imperiled  sandstones.  There  are  also  some 
Cdlcareous  beds  in  the  system,  but  these  ure  not  regularly 
developed,  and  are  all  siliceous  and  concretionary  in  their 
composition  and  texture.  From  their  impure  and  concre- 
tionary aspect,  they  are  generally  known  by  the  name  of 
cornstones,  and  are  of  little  or  no  use  as  limestones.  Taken 
iii  the  mass,  the  composition  of  this  system  is  sufficiently 
indicated  by  the  term  old  rtd  sandstone — the  epithet  "  old" 
bv  ing  applied  to  distinguish  it  from  another  series  of  red 
sandstones  which  occurs  above  the  coal  measures,  and  is 
usually  designated  the  new  red  sandstone. 

472.  What  is  said  of  the  order  of  its  succession? 

473.  What  is  the  composition  and  variety  of  this  sandstone,? 

474.  To  what  is  its  colour  ascribed  ? 


OLD  RED  SANDSTONE  SYSTEM.  .123 

[When  sand  is  found  cemented  together  by  iron  or  car- 
bonate of  lime  which  has  been  infiltrated  through  the  mass 
in  a  state  of  solution,  thus  forming  compact  stones,  it  has 
been  called  alluvial  sandstone.  When  rounded  pebbles  are 
thus  cemented,  they  form  conglomerate  or  puddingstone; 
and  if  the  mass  be  composed  of  angular  fragments,  it  is 
called  breccia.  Of  this  variety,  the  beautiful  pillars  in  the 
interior  of  the  Capitol  of  the  United  States,  at  Washington 
are  built.] 

1  72.  77ie  order  of  succession  among  the  old  red  sandstone 
strata  varies  considerably  in  different  localities.  It  has 
been  stated  that  the  prevailing  mineral  characters  are  —  fine- 
grained red  sandstones,  including  detached  pebbles;  beds 
of  coarse  conglomerate  ;  fine-grained  fissile  micaceous  beds 
of  a  gray  colour,  locally  called  tilestones  and  flagstones; 
layers  of  mottled  shales;  arid  strata  of  yellow  sandstone. 
Now,  although  in  some  districts  the  conglomerate  may  be 
undermost,  and  in  others  the  tilestones,  yet,  making  allow- 
ance for  these  local  deviations,  the  following  may  be  taken 
as  the  most  frequent  order  of  occurrence:  — 

COAL  MEASURES  :  - 

1.  Yellow  sandstones,  fine-grained,    including  detached   peb- 
bles,  and  alternating  with  layers  of  mottled  shale.    Remains 
of  fishes,  but  no  traces  of  vegetables. 

2.  Red  conglomerate,  or  Puddingstone,  of  vast  thickness,  either 
in  one  mass,  or  interrupted  by  occasional  beds  of  red  sand- 


g 

<  K 

a  ^ 

D  > 

£  ^ 


stone.     No  organic  remains 


3.  The 
red 


red  sandstone  proper,  generally  in  thick  beds  of  a  brick- 
colour,  enclosing  detached  pebbles  of  quartz  and  other 
primary  rocks.     Conglomerate  beds  and  concretionary  lime- 
stones  are  occasionally  interstratified.    Organic  remains  rare, 
and  not  very  distinct. 

4.  Gray  micaceous  beds,  sometimes  dark  and  bituminous.  These 
vary  in  thickness,  from  one  inch  to  several  feet.  Remains  of 
fishes  abundant;  some  vegetable  impressions. 

GRAUWACKE. 

The  preceding  synopsis  represents  the  usual  order  of  the 
system  as  it  occurs  in  Scotland.  All  of  these  groups  are 
well  marked  in  the  field  ;  and  when  treated  not  as  distinct 
systems,  but  as  portions  of  one  great  system,  materially  aid 
the  investigations  of  the  geologist. 

47o.   What  of  the  order  of  succession  T 
476.  Explain  the  tabular  arrangement. 


124  GEOLOGY. 

173.  The  organic  remains  of  the  system,  if  not  so  numer- 
ous as  those  of  the  grauwacke  beneath,  or  the  carboniferous 
measures  above,  are  at  least  equally  interesting,  on  account 
of  their  peculiarities  and  adaptation  to  the  conditions  under 
which  they  were  destined  to  exist.     The  remains  of  plants 
are  few  and  indistinct ;   but  are  apparently  allied  to  those 
found  in  the  true  silurian  rooks.     In  the  tilestone  group 
have  been  found  impressions  of  ferns,  equisetaceaB,  leaves 
resembling  those  of  the  flag  and  flowering  rush,  and  circu- 
lar markings  like  the  floral  envelopes  or  berries  of  some 
shrubby  plant.     Most  of  these  are  highly  carbonized  and 
broken,  as  if  drifted  from  a  distance  by  water,  and  deposited 
among  the  sandy  material  in  which  they  are  now  imbedded. 
A  few  carbonaceous  layers  occur  among  the  schistose  beds; 
but  vegetable  matter  nowhere  abounds  in  sufficient  quantity 
to  form  bituminous  layers  or  thin  seams  of  coal.     Taken 
as  a  whole,  the  old  red  sandstone  system  is  particularly 
barren  of  vegetable  remains,  and  seems  to  evince  a  condi- 
tion of  the  earth  which  did  not  permit  of  the  growth  of 
plants  unless  in  detached  and  limited  areas;  these  plants 
being  by  no  means  high  in  the  scale  of  vegetable  organiza- 
tion.    Its  animal  remains  are  more  abundant  and  distinct; 
but  present  little  variety — the  prevailing  types  being  marine 
fishes  of  simple  but  curious  structure. 

174.  The  fossil  Jishes,  or  ichthyolite$,ofthe  old  red  sand- 
stone, present  the  first  distinct  trace  of  the  existence  of  the 
highest  division  of  the  animal  kingdom;  namely,  vertebrata. 
It  must  be  remarked,  however,  that  the  earliest  genera  are 
not  of  the  most  perfect  structure;    but  form,  as  it  were,  a 
link  between  the  humbler  Crustacea  and  fully-developed 
fishes.     The  cephalaspis,  coccosteus,  and  ptericthys,  repre- 
sented in  the  following  engraving,  are  the  most  prominent 
types  of  these  crustacean-like  families.     The  cephalaspis, 
in   general  figure,  resembles  the  asapkus  of  the  silurian 
rocks,  is  covered  with  bony  plates,  and  takes  its  name  from 
the  buckler-shape  of  its  head  (Gr.,  Icrphale.,  the  head,  and 
aspis,  a  buckler).     The  coccosteus  is  also  enveloped  in  a 

477.  What  variety  of  organic  remains  are  found  ? 

478.  What  of  its  fossil  fishes  ? 

479.  Describe  their  peculiarities  and  uaiaes. 


OLD  RED  SANDSTONE  SYSTEM. 


120 


bony  covering,  is  furnished  jvith  a  tail  for  locomotion,  and 
takes  its  name  from  the  berry-like  tubercles  which  dot  its 
plates  (Gr.,  kokkos,  a  berry,  and  osteon,  a  bone).  The 
ptericthys  has  the  same  kind  of  covering  or  external  skele- 
ton :  but  its  distinguishing  feature  is  a  pair  of  wing-like 
appendages,  which  seem  not  only  to  have  aided  in  locomo- 
tion, but  to  have  reared  defensively  when  attacked.  It 
takes  its  name  from  these  appendages  (Gr.,p/mw,  a  wing, 
and  ichthys,  a  fish),  and  is  one  of  the  most  abundant  fossils 
in  this  formation — being  as  characteristic  of  the  old  red 


1.  Cephalaspis.  2.  Coccosteus.  3.  Ptericthys. 

sandstone  as  the  trilobite  was  of  the  silurian  rocks.  In  the 
holitpfychius  (figure  on  next  page),  and  some  others,  this 
bony  covering  prevails;  but  it  is  formed  of  a  greater  number 
of  plates  finely  enameled  and  curiously  engraven,  while  the 
general  outline  of  the  figure  more  closely  approximates  to 
that  <f  existing  fishes,  with  a  tail  arid  fins  as  organs  of  loco- 
n  oti ->n.  In  other  genera,  the  plates  pa<s  by  gradations  into 
bony  scales,  regularly  arranged,  so  as  to  join  or  overlap 


480.   Explain  the  dii?ram  on  this  page. 


GEOLOGY. 


Holoptychius  Nobilissimus. 

each  other.  This  structure  is  well  illustrated  by  the  osteole- 
pis  (Gr.,  osteon,  a  bone,  and  lepis,  a  scale),  which  presents 
the  form  of  a  perfect  fish  furnished  with  pectoral,  abdomi- 
nal, and  caudal  fins.  In  the  osteolepis  (see  figure)  the 
bony  scales  are  placed  alongside  each  other  like  the  bricks 
in  a  building ;  calculated  at  once  to  afford  a  strong  protec- 
tion to  the  internal  parts,  and  to  yield  to  the  bendings  of 
the  body  while  in  motion.  In  the  previous  forms  of  animal 
life,  the  organs  of  motion  are  but  imperfectly  developed; 


Osteolepis. 

but  in  the  osteolepis  a  great  advance  is  exhibited,  its  fins, 
tail,  and  elongated  form  of  body  being  such  as  to  combine 
strength  with  agility.  Some  families  of  these  early  fishes 
are  furnished  with  spiny  fins,  or  are  otherwise  armed  with 
detached  spines  from  two  to  five  inches  in  length,  and 
which  are  known  to  geologists  by  the  name  of  ichthy odont- 
lites  (Gr.,  ichthy f,  a  fish,  doru,  a  spear,  and  litlios,  a  stone). 
In  all  of  them  the  tail  is  unequally  lobod,  like  that  of  the 
shark — a  character  which  distinguishes  cartilaginous  from 

481     Whnt  do  these  diagrams  exhibit/ 


OLD  RED  SANDSTONE  SYSTEM.  127 

osseous  fishes ;  the  shark,  dog-fish,  sturgeon,  &c.  belong- 
ing to  the  former,  the  cod,  herring,  salmon,  &c.  to  the  lat- 
ter division.  (Par.  181.) 

175.  From  what  we  have  seen  of  the  fossil  flora  and  fauna 
of  this  system,  they  seem  to  indicate  a  condition  of  life 
higher  in  point  of  development  than  that  which  existed 
during  the  deposition  of  the  grauwacke  and  silurian  rocks. 
The  cephalaspis,  coccosteus,  and  ptericthys,  are  successive 
advances    upon   the   simply   organized  asaphus;    and   the 
lioloptychius,  osteolepis,  and  glyptolepis,  belong  to  orders 
still  more  fully  developed  than  the  ptericthys.     But  while 
this  advance  in  the  scale  of  organization  took  place,  some 
peculiarity  in  the  waters  of  the  ocean,  or  other  condition, 
seems  to  have  prevented  the  increase  of  previously  existing 
orders ;  for  in  none  of  the  beds  of  the  old  red  sandstone  do 
we  find  the  corals,  shell-fish,  and  Crustacea  of  the  silurian 
system.     It  is  true  that  in  the  lower,  or  flagstone  series, 
remains  of  crustaceans  have  been  discovered;  but  in  such 
an  imperfect  state,  that  it  is  impossible  to  decide  what  ana- 
logy they  bear  to  those  of  the  silurian  limestones.     Again, 
the  vegetation  which  existed  during  the  formation  of  the 
grauwacke  rocks  seems  to  have  vanished  almost  entirely 
while  the  deposition  of  the  old  red  sandstone  was  going 
forward ;  for,  unless  at  a  few  detached  points,  do  we  find 
anything  like  a  vegetable  organism  throughout  the  whole 
mass  of  the  formation. 

1 76.  The  conditions  of  the  world  during  the  deposition  of 
the  old  red  sandstone  are  but  imperfectly  indicated  by  the 
fossil  organisms  to  which  we  have  adverted.    Flanking  the 
primary  and  transition  hills,  the  old  red  sandstone  is  emi- 
nently a  littoral  deposit,  the  lower  or  gray  micaceous  series 
evincing  sediment  in  calm  water,  the  sandstone  and  con- 
glomerate beds  the  action  of  currents  and  other  aqueous 
agitation,  and  the  yellow  beds  a  recurrence  of  calm  depo- 
sition.    Many  of  the  strata  present  the  ripple  mark  of  the 
tide  as  perfect  as  that  now  to  be  traced  on  the  sands  of  the 
existing  shore;  and  the  conglomerate  throughout  its  entire 

482.  What  is  the  geological  reasoning  touching  this  period,  based 
Hoon  its  fossils  ? 

4SJ3.  What  of  the  conditions  of  the  globa  at  this  period  T 


128 

composition  points  to  causes  analogous  to  those  by  which 
the  gravel-beaches  of  the  present  day  are  collected.  The 
colouring  matter  (peroxide  of  iron)  of  the  formation  shows 
that  the  waters  must  have  been  impregnated  with  mineral 
solution,  so  as  to  be  deleterious  to  animal  life;  and  it  is  a 
curious  corroboration  of  this  fact,  that  the  fossil  fishes  are 
most  abundantly  found  in  the  flagstone  and  yellow  sand- 
stone series — the  strata  least  coloured  by  the  metallic  im- 
pregnation. Whence  the  metallic  oxide  was  obtained  by 
which  the  formation  is  more  or  less  tinged  throughout,  is  a 
matter  of  hypothesis  among  geologists;  but  that  opinion 
which  ascribes  it  to  volcanic  origin  is  the  most  commonly 
entertained,  and  indeed  the  only  one  which  seems  adequate 
to  account  for  the  phenomenon.  If,  then,  the  old  red  sand- 
stone period  was  one  of  extraordinary  volcanic  disturbance, 
rendering  the  earth  and  atmosphere  less  capable  of  nourish- 
ing an  abundant  vegetation,  and  poisoning  the  waters  against 
the  development  and  propagation  of  animal  life,  the  student 
may  readily  perceive  why  organic  remains  should  be  so 
scantily  disseminated  through  its  material,  even  while  an 
advance  was  being  made  in  the  kind  and  character  both 
of  vegetable  and  animal  existence. 

177  The  igneous  rock*  associated  with  the  system,  and 
by  which  it  has  been  upheaved  into  its  present  position, 
are  greenstone,  claystone,  porphyry,  felspar,  amygdaloid, 
and  many  other  varieties  of  trap.  Occasionally,  the  trap  is 
cut  through  by  dykes  of  more  recent  greenstone,  felspar, 
and  serpentine;  but  true  granitic  rock  is  seldom  or  ever 
in  intimate  connexion  with  any  portion  of  the  series.  By 
the  termination  of  the  old  red  sandstone  deposit,  the  gra- 
nitic igneous  era  may  be  said  to  have  passed  away,  and  to 
have  been  succeeded  by  that  of  the  trap — an  era  which 
produced  more  complicated  displacements  and  contortions 
of  the  stratified  rocks,  though  less  extensive  and  gignntic 
elevations.  In  Scotland,  the  Grampians  belong  to  the 
former  era,  the  Ochils  to  the  latter ;  two  ranges  which, 
even  to  the  untutored  eye,  present  so  many  points  of  dis- 

484.  How  is  the  iron  accounted  for  ? 

485.  What  igneous  rocks  are  found  here  1 
4S6.  What  of  the  trap  era  of  the  globe  ? 


OLD  RED  SANDSTONE  SYSTTM.  129 

similarity  both  in  their  external  contour  and  internal  com- 
position, as  at  once  to  be  ascribed  to  different  eras.  The 
volcanic  forces  which  were  smouldering  throughout  the 
whole  formation  of  the  old  sandstone,  seem,  at  the  conclu- 
sion of  the  deposit,  to  have  spent  themselves  in  one  gigantic 
paroxysm,  and  to  have  upheaved  the  newly-consoiidated 
strata  into  mountain  ridges  of  extreme  irregularity,  along 
whose  flanks,  as  they  extended  seaward,  were  deposited 
unconformably  the  strata  of  the  succeeding  formation. 

178.  The  extent  of  country  occupied  by  the  old  red  sand- 
stone is  very  great,  owing,  in  many  instances,  to  the  flat 
position  of  the  strata,  which  thus  cover  a  larger  amount  of 
surface  than  they  would  have  done  had  they  been  highly 
inclined  like  the  primary  formations.     All  the  members  of 
the  series  are  widely  developed   in  Scotland ;   the  lower 
portions  occur  between  England  and  Wales,  in  Ireland, 
and  in  Germany;    the  middle  portions  occupy  extensive 
areas  in  Russia  and  the  flats  of  Central  Europe,  in  Siberia 
and  Tartary,  and  flank  also  the  southern  Himmalehs;  and 
different  members  of  the  system  occur  in  various  districts 
of  North  and  South  America,  as  well  as  in  Central  Africa. 

1 79.  The  geographical  features  of  red  sandstone  districts 
are  in  general  varied  and  irregular;    the  hills  being  less 
bold  and  precipitous  than  those  of  primary  formations,  and 
more  lofty  and  undulating  than  those  of  any  subsequent 
period.     Where  the  strata  lie  flat,  and  comparatively  un- 
broken, the  scenery  is  rather  uninteresting;  but  the  soil  is 
light  and  fertile,  being  based  on  sand,  gravel,  or  reddish 
clay,  composed  of  the  debris  of  the  formation.     On  the 
other  hand,  the  mountains  of  the  old  red  sandstone  exhibit 
great  diversity  of  scenery:  rising  in  easy  undulations,  sink- 
ing and  swelling  in  every  direction,  yet  preserving  a  com- 
mon continuity  of  range,  they  present  in  the  chain  a  suc- 
cession of  rounded  heights  and  cones;  but  in  the  mass,  an 
irregular  surface  of  hills  and  valleys,  glens  and  recesses,  of 
great  beauty  and  amenity.     The  Ochils  and  Sidlaws,  in 
Scotland,  with  their  intervening  valleys,  belong  exclusively 


487.  What  of  the  localities  and  extent  of  this  system  T 
4^8.  What  of  itt  physical  geography  ? 


130 


GEOLOGY. 


to  this  formation,  and  may  be  taken  as  the  type  of  its  phy- 
sical features. 

ISO.  The  minerals  of  commerce  derived  from  the  old  red 
sandstone  are  comparatively  few.  From  the  lower  group 
of  beds  are  obtained  those  thin  schists  of  gray  micaceous 
sandstone  so  generally  employed  in  foot-pavements,  in 
roofing  and  in  flooring;  hence  the  terms  tilestone  &n<\  flag- 
stone. From  the  superior  red  and  yellow  groups,  building- 
stones  of  various  qualities  are  obtained  ;  but  none  of  these 
are  of  great  beauty  or  durability.  The  claystone,  porphy- 
ries, and  felspars,  are  exceedingly  durable ;  but  are  seldom 
used  by  the  builder,  owing  to  the  difficulty  of  hewing  them 
into  form.  From  the  trap,  some  of  the  best  material  for 
macadamizing  is  obtained  in  the  lowlands  of  Scotland ; 
while  among  the  debris  of  the  same  rocks,  the  lapidary 
finds  many  geodes  of  the  finest  chalcedonies,  agates,  jas- 
pers, and  carnelians. 

CLASSIFICATION  OF  FOSSIL  FISHES. 

181.  Before  proceeding  with  our  description  of  the  suc- 
ceeding formations,  it  will  be  necessary  to  advert  to  the 
system  of  classification  which  has  been  adopted  in  reference 
to  fossil  fishes,  inasmuch  as  it  differs  from  that  which  Cuvier 
applied  to  existing  races.  This  celebrated  naturalist  col- 
lected the  whole  number  of  species  into  two  groups,  ac- 
cording to  the  nature  of  the  skeleton  and  the  hard  parts — 
one  group  embracing  the  OSSEOUS,  or  bony,  and  the  other 
the  CARTILAGINOUS  fishes.  The  former  group  he  further 
separated  into  two  orders — the  Acanthopttrygian,  or  thorny- 
finned,  and  the  Malacopterygian,  or  soft-firmed.  This  me- 
thod, however,  does  not  meet  the  wants  of  the  geologist, 
because  the  skeleton  is  seldom  or  ever  found  in  such  a 
state  as  to  answer  the  purposes  of  classification  Fossil 
scales,  teeth,  spines,  and  fragments  of  fishes,  are  found  in 
abundance,  but  these  afford  too  imperfect  data  for  arrange- 
ment; and  when  an  eirtire  specimen  occurs,  it  is  merely 

489.  What  ofits  economical  uses  1 

490.  What  was  Cuvier's  groups  of  fishes? 

491.  Why  will  this  system  fail  to  arrange  fossil  fishes  ? 


CLASSIFICATION  OF  FOSSILS.  131 

the  genera]  shape  and  character  of  its  scaly  covering  upon 
which  the  ichthyologist  can  decide  with  certainty.  Pro- 
ceeding upon  this  principle,  M.  Agassiz  takes  the  dermal 
covering  as  the  foundation  of  his  system — the  skin  being 
that  organ  which  indicates  not  only  important  structural 
and  functional  difference?,  but  also  shows  the  relation  of 
every  animal  to  the  element  in  which  it  moves.  (Appen.) 
182.  Instead  of  the  divisions  Osseous  and  Cartilaginous, 
he  disHngitifkes  Jmtr  great  orders  ofjishes  according  to  the 
nature  of  their  scales,  and  finds  that  other  important  dis- 
tinctions of  structure,  &/c.  harmonize  with  these  differences 
of  scales.  This  discovery  is  invaluable;  for,  of  all  parts  of 
fishes,  the  scales  are  those  most  abundantly  found  in  a  fos- 
sil state;  and  if  by  a  single  scale  the  geologist  can  detect 
the  order  to  which  any  fish  belonged,  he  has  also  a  clue  to 
its  habits  and  mode  of  life,  and  to  the  conditions  under 
which  it  flourished.  The  following  is  a  sketch  of  the  prin- 
cipal divisions  and  subdivisions  proposed  by  M.  Agassiz: — 

I. SCALES  ENAMELED. 

1.  GANOIDIANS  (Gr.,  ganos,  splendour,  from  the  bright  surface  of  their 

enamel). — The  fishes  of  this  order  are  covered  with  angular  scales, 
composed  internally  of  bone,  and  coated  with  enamel.  The  scales 
are  regularly  arranged,  and  entirely  cover  the  skin.  The  sauroid 
fish,  or  those  which,  from  the  structure  of  their  teeth  and  other 
peculiarities,  approximate  to  reptiles,  are  amongst  the  most  inte- 
resting of  this  order.  Nearly  all  the  species  referred  to  it  are 
extinct;  the  sturgeons,  and  bony-pike  of  the  North  American  lakes, 
are  living  examples. 

2.  PLACOIDIANS  (Gr.,p/ax,  a  broad  plate). — Fishes  of  this  order  have 

their  skin  covered  irregularly  with  plates  of  enamel,  often  of  con- 
siderable dimensions,  but  sometimes  reduced  to  small  points,  like 
the  shagreen  on  the  skin  of  the  shark,  and  the  prickly  tubercles 
of  the  ray.  It  comprehends  all  the  cartilaginous  fishes  (sharks  and 
rays),  with  the  exception  of  the  sturgeon. 

II. SCALES  NOT  ENAMELED. 

3.  CTENODIANS  (Gr.,  kteis,  genitive  ktenos,  a  comb) — Ctenoid  fishes 

have  their  scales  of  a  horny  or  bony  substance  without  enamel, 
jagged  like  the  teeth  of  a  comb  on  the  outer  edge.  The  perch, 
ana  many  other  existing  genera,  are  of  this  order,  which  contains 
but  few  fossil  forms. 

492.  What  is  Agassiz's  method,  and  how  many  orders  of  scales? 

493.  Explain  his  divisions  and  subdivisions 


132 


GEOLOGY. 


4.  CYCLOIDIANS  (Gr.,  cyclos,  a  circle). — The  fishes  of  this  order  have 
smooth,  horny,  or  bony  unehameled  scales,  entire  at  the  margin, 
with  concentric  or  other  lines  on  the  upper  surface.  The  herring, 
salmon,  &c.  belong  to  this  order,  which,  along  with  the  former, 
includes  almost  the  whole  number  of  existing  species. 

Such  are  the  divisions  proposed  by  M.  Agassiz,  and  now 
universally  adopted  by  geologists,  although  it  is  not  unlikely 
that  a  more  perfect  system  may  soon  be  propounded,  which 
will  embrace  in  one  category  both  fossil  and  existing  species. 
M  he  subjoined  engraving  more  summarily  represents  the 
i'our  orders  of  scales  above  al'uded  to: — 


1.  Ganoid;  2.  Placoid ;  3.  Ctenoid;  and,  4.  Cycloid,  Scales. 
183.  Each  of  these  ordrrs  contains  both  bony  and  cartila- 
ginous fishes.  The  representatives  of  each  prevailed  in 
different  proportions  during  different  epochs;  the  two  first 
(enameled  scales)  existed  be'ore  the  commencement  of  the 
chalk  system ;  the  third  and  fourth  orders,  which  contain 
nearly  five-sixths  of  living  species,  appear  for  the  first  time 
in  the  chalk  strata,  when  all  the  preceding  fossil  genera  of 
the  two  first  orders  had  become  extinct.  Another  remark- 
able circumstance  observed  by  M.  Agassiz  is,  that  all,  rr 
nearly  all,  the  fossil  fishes  found  in  strata  beneath  the  mag- 


l.  Heterocercal,  or  Unequally  bilobate;    2.  Equally  bilobate ;   and, 
3.  Single  and  rounded,  forms  of  tail. 

494.  What  of  the  diagrams  here  given  ? 

495.  What  different  epochs  are  represented  ? 

496.  Define  the  terms  and  explain  the  diagrams. 


EXPLANATORY   NOTE.  133 

nesian  limestone  are  heterpctrcal,  that  is,  have  their  tails 
unequally  bilobate  (see  fig.),  like  the  shark,  sturgeon,  lepi- 
dosteus,  &c.;  while  this  form  of  tail  is  rarely  found  in  the 
oolite  and  superior  strata.  Among  existing  fishes,  the  tail, 
or  caudal  fin,  is  generally  equally  bilobate,  as  in  the  trout ; 
or  single  and  rounded,  as  in  the  wrasse ;  but  seldom  hete- 
rocercal.  This  latter  form  is  produced  by  a  remarkable 
prolongation  of  the  vertebra,  which  bears  a  striking  ana- 
logy to  the  prolongation  of  the  same  parts  in  reptiles;  thus 
connecting  the  cartilaginous  fishes  with  the  reptilia,  not 
only  by  internal  structure,  but  also  by  the  evidences  of  ex- 
ternal form. 

EXPLANATORY    NOTE. 

OLD  RED  SANDSTONE. — To  this  system  English  geologists  sometimes 
apply  the  term  "  Devonian,"  because  it  happens  to  be  very  exten- 
sively developed  in  Devonshire.  Distinctions  of  this  kind  are  always 
objectionable,  and  particularly  in  the  present  instance,  where  the 
general  term,  Old  Red  Sandstone,  is  so  eminently  descriptive. 

PEROXIDE  OF  IRON. — When  the  oxygen  of  common  air  unites  with 
the  atoms  of  iron,  an  oxide,  or  rust,  of  iron  is  the  result ;  and  when 
this  rust  has  absorbed  as  much  oxygen  as  it  is  capable  of,  it  is  then 
termed  a  peroxide,  or  thorough  oxide,  of  iron. 

ICHTHYOLITE  (Gr.,  ichthys,  a  fish,  and  lithos,  a  stone). — A  fish,  or  any 
part  of  a  fish,  found  in  a  fossil  state,  is  termed  an  ichthyolite. 

PUDDINGSTONE — any  conglomerate  of  rounded  pebbles  cemented 
together  by  a  silicious  or  sandy  paste.  When  select  specimens  are 
cut  and  polished,  they  resemble  a  section  of  plum-pudding;  hence  the 
term  puddingstone. 

PORPHYBY  (Gr.,  porphyra,  purple). — This  term  was  originally  applied 
to  a  reddish  unstratified  rock  found  in  Egypt,  and  used  by  the  ancients 
for  statuary  purposes.  It  is  now  employed  by  geologists  to  denote  a 
reddish  igneous  rock  containing  imbedded  crystals  of  felspar ;  and  all 
rocks  (whatever  their  colour)  which  contain  imbedded  crystals  distinct 
from  their  mass,  are  said  to  be  porphyritic.  We  have  thus  felspar, 
porphyry,  porphyritic  granite,  and  porphyritic  greenstone. 

AMYGDALOID (Gr.,amygdalon,  an  almond,  and  eidos,  a  form) — almond- 
shaped.  The  term  is  applied  to  certain  trap  rocks  in  which  other 
minerals  are  occasionally  imbedded  like  almonds  in  a  cake.  Some 
varieties  of  amygdaloid  are  locally  termed  toad-stones,  from  the  resem- 
blance which  their  colour  and  makings  bear  to  that  of  a  toad's  skin. 

GEODES  (Gr.,  geodcs,  earthy) — a  term  applied  to  rounded  pebbles 
having  an  internal  cavity  lined  with  crystals;  also  to  rounded  or 
nodular  pebbles  themselves  ;  and  to  nodules  of  ironstone  hollow  in  the 
centre. 

497.  Explain  the  the  terms  of  the  note.  / 

498    Define  the  terms  of  the  note. 


134  GEOLOGY. 

CARBONIFEROUS  SYSTEM. 

184.  At  the  close  of  the  Old  Red  Sandstone  period  the 
earth  seems  to  have  undergone  an  almost  total  change  in 
its  geological  conditions.    The  red  sandstones  and  gravelly 
conglomerates  which  had  been  formed  along  the  shores  and 
bottom  of  the  sea,  were  upheaved  into  dry  land;   thus  add- 
ing to  the  extent  of  land  previously  existing,  and  gradually 
circumscribing  the  limits  of  the  ocean  in  which  subse- 
quent deposits  were  to  take  place.     As  disintegrated  gra- 
nite furnished  the  felspar,  quartz,  and  mica  of  the  gneiss 
and  mica  schist,  and  as  from  these,  again,  were  obtained 
the   materials  of  the  clay-slate,  grauwacke,  and   silurian 
rocks,  so  from  all  these,  together  with  the  newly  upheaved 
red  sandstone,  were  derived  the  material  of  the  succeeding 
formation.    These  successive  attritions  would  reduce  quartz 
to  sand  of  various  fineness,  felspar  to  loose  impalpable  clay, 
mica  from  large  plates  to  minute  scales,  and  crystalline 
limestone   to  a  dully  powdery   consistence.       The   rocks 
formed  of  these  ingredients  would  necessarily  present  a  less 
compact  texture;  arid  thus  it  is  in  the  Carboniferous  System 
that  the  sandstones  are  more  arenaceous,  the  shales  soft  and 
earthy,  and  the  limestones  non-crystalline  and  often  impure. 
Besides  the  sandstone,  clay,  and  limestone,  two  new  rock 
substances  make  their  appearance  among  the  strata  of  this 
system,  namely,  coal  and  ironstone — the  former  being  the 
result  of  compressed  and  altered  vegetation,  and  the  latter 
a  chemical  aggregation  of  the  metallic   particles   around 
some  earthy  basis.     The  iron  of  the  old  red  sandstone  was 
disseminated  through  the  mass  as  mere  colouring  matter ; 
in  the  carboniferous  formation  it  is  principally  collected  in 
layers,  or  in  nodules.     The  vegetation  of  previous  periods 
was  so  scanty  as  to  leave  only  a  few  dubious  impressions 
among  the  strata.     During  the  era  about  to  be  considered, 
it  was  so  abundant,  as  to  form  numerous  beds  of  coal,  rang- 
ing in  thickness  from  a  few  inches  to  twenty  or  even  thirty 
feet. 

185.  The  term  "Carboniferous"  has  been  applied  to  this 

499.  To  what  system  do  coal  and  ironstone  belong  1 
i)00.  What  is  the  source  aiH  nature  of  each ? 


MOUNTAIN,  OR  CARBONIFEROUS   LIMESTONE.  1JV> 

system  from  the  fact,  that  vegetable  deposits — of  which  the 
main  solid  element  is  carbon — constitute  its  most  distin- 
guishing feature.  It  is  regarded  by  many  as  marking  the 
commencement  of  the  SECONDARY  PERIOD;  and  holds  a 
position  in  the  earth's  crust  intermediate  between  the  old 
and  new  red  sandstones.  Having  been  deposited  after  the 
upheaval  of  the  old  red  sandstone,  it  rests  in  many  places 
unconformably  upon  that  system,  and  occupies  smaller  and 
more  detached  areas,  which  often  assume  a  basin  or  trough 
lorm,  as  shown  in  par.  201.  It  is  composed  of  two  very 
distinct  groups,  the  mountain  limestone  and  the  coal  mea- 
sures, which  in  some  respects  require  separate  descriptions. 

MOUNTAIN,  OR  CARBONIFEROUS  LIMESTONE. 

186.  The  distinguishing  feature  in  the  mineral  composi- 
tion of  this  group  is  sufficiently  indicated  by  the  name 
Mountain  Limestone.  It  must  not  be  supposed,  however, 
that  it  is  entirely  composed  of  calcareous  beds ;  but  merely 
that  the  limestones  are  the  most  characteristic  members; 
for  many  of  the  inferior  strata  are  pure  quartzose  sand- 
stones, containing  scarcely  a  trace  of  lime,  and  alternating 
with  thin  seams  of  coal  and  bituminous  shales.  As  deve- 
loped in  the  British  islands,  the  group  may  be  said  to  con- 
sist of  thick-bedded  gray  or  bluisli  sub-crystalline  lime- 
stones, divided  by  partitions  of  grits  and  shales,  and  of 
whitish  quartzose  sandstones  of  various  fineness,  separated 
by  subordinate  layers  of  shale,  thin  seams  of  coal,  and  bands 
oi  ironstone.  It  is  generally  found  flanking  or  crowning 
the  trap-hills  which  intervene  between  the  old  red  sandstone 
and  coal  measures,  presenting  bold  escarpments;  hence 
the  term  mountain  limestone.  The  epithet  carboniferous 
is  also  applied  to  it,  because  it  invariably  underlies  the  true 
coal  measures  wherever  these  occur,  and  is  generally  asso- 
ciated with  thin  seams  of  coal  and  bituminous  shales.  Like 
all  stratified  rocks,  this  is  broken  up  by  fissures  and  dislo- 
cations caused  by  subterranean  movements;  but,  indepen- 

501.  What  difference  in  the  metal  and  vegetation  of  this  system! 

502.  Of  what  two  groups  is  it  composed  T 

503.  What  is  the  nature  of  mountain  limestone  I 
604.  What  relation  has  it  to  the  seams  of  coal? 


I  '10  OKOLOGY. 

dently  of  these,  it  is  numerously  intersected  by  what  are 
termed  joints  and  divisional  planes  —  the  former  being  rents 
(or  backs,  as  they  are  called  by  quarrymen)  perpendicular 
to,  and  the  latter  partings  parallel  with,  the  plane  of  strati- 
fication. 

187.  The  order  of  succession  among  the  strata  of  this 
group  is  by  no  means  determinate.    In  some  districts,  only 
a  few  beds  of  calcareous  shales  and  grits  occur  between 
the  limestone  and  old  red  sandstone;  in  others,  a  vast  suc- 
cession  of  white    quartzose    sandstones    alternating    with 
bituminous  shales,  thin  seams  <  f  coal,  and  bands  of  iron- 
stone ;  while  in  Fife  and  Mid-Lothian,  these   sandstones 
are  associated  with  strata  of  shell  and  fresh-water  (?)  lime- 
stone.    Whatever  may  be  the  character  or  thickness  of 
the  rocks  beneath,  the  true  mountain  limestone  of  itself 
constitutes    a   well-marked    suite    of  strata,    easily   distin- 
guishable from  any  other.     Sometimes  it  consists  of  two, 
four,  or  six  beds,  divide'!  by  partings  of  argillaceous  mat- 
ter; at  other   times  the  beds  are  separated  by  layers  of 
calcareous  sandstone  and  shale;   while  riot  unirequently  it 
occurs  in  one  mass  of  vast  thickness,  flanking  some  trap- 
hill  precisely  aiter  the  manner  in  wrhich  a  coral  reef  skirts 
the  island  around  which  it  is  forming.     In  general,  there 
occur  above  the  limestone  calcareous  shales,  sandstones, 
and  thin  seams  of  coal,  which  pass  into  the  true  coal  mea- 
sures ;   but  in  the   north  of  England,  there  intervenes  a 
series  of  very  pebbly  or  quartzose  sandstones,  known  by 
the  name  of  Millstone  Grit.     Notwithstanding  these  vari- 
ations, the  calcareous  members   gradually  disappear,  and 
the  carboniferous  become  more  frequent  as  we  ascend,  so 
that  there  is  no  great  difficulty  in  fixing  the  line  of  demar- 
cation between  the  two  groups. 

188.  The  organic  remains  of  the  mountain  limestone  are 
eminently  marine.     It  is  true  that  the  occurrence  of  thin 
seams  of  coal  attest  the  presence  of  terrestrial  plants  which 
must  have  been  drifted  into  the  sea  of  deposit  ;  and  there  is 
some  doubt  among  geologists  as  to  the  origin  of  certain 


505.  What  variety  of  strata  occurs  in  this  group  ? 

506.  Where  occurs  the  millstone  grit  1 


MOUNTAIN,  OK  CARBONIFEROUS  LIMESTONE.  I  :}7 

limestones  among  the  lower  strata;  but  laying  these  aside, 
the  whole  character  of  the  group  is  as  decidedly  oceanic  as 
the  living  coral  reefs  of  the  Pacific.  The  most  remarkable 
advance  upon  the  marine  life  of  former  periods,  as  <  vi- 
denced  by  the  Ibssils  of  the  mountain  limestone,  is  that 
which  appears  among  the  Radiata.  In  the  silurian  r«cksf 
the  corals  were  chiefly  of  a  sessile  kind ;  in 
this  group  many  of  them  are  free  and  inde- 
pendent animals,  bearing  little  or  no  analogy 
either  to  previous  or  existing  forms.  The 
most  prevalent  of  these  was  the  Crinoid  or 
Encrinitf  family,  of  whose  exuviae  many  bed* 
of  limestone  are  almost  wholly  composed. 
Of  the  encrinite  (Gr.,  krine,  a  lily),  or  lily- 
shaped  corals,  are  found  many  genera  and 
sub-genera  —  the  distinctions  being  made 
from  the  external  figure  of  the  stalk  and 
head.  That  exhibited  in  fig.  A  may  be  taken 
as  the  type  of  the  class ;  it  is  the  encrinitcs 
nionilifurmis,  so  called  from  the  necklace- 
shape  of  its  stalk.  Besides  the  encrinites 
moniliformis,  which  is  by  far  the  most  pre- 
valent of  the  crinoideans,  there  were  the 
pentairinus,  five-sided  instead  of  round,  the 
actinocrinus,  or  spiny  encrinite,  the  ajrincri- 
nite,  so  called  from  the  pear-like  form  of  its 
head,  and  many  others  deriving  their  names 
from  similar  distinguishing  features.  By 
examining  fig.  A,  the  student  will  perceive 
that  the  encrinite  consisted  of  a  stalk  com- 
posed of  numerous  joints,  rendered  flexible 
by  means  of  cartilage,  and  perforated  for  the 
passage  of  an  internal  canal ;  that  it  was 
fixed  at  its  base,  and  supported  at  its  free 
extremity,  a  cup-like  body(s)  containing  the 
mouth  and  stomach;  that  this  cup-like  body  was  composed 

607.  What  of  the  fossils  found  in  this  group  ? 

50^.  Of  what  families  are  the  remains  of  animals  here  ? 

509.  What  is  represented  in  the  diagram  T 

510.  Describe  this  singular  animal. 


138  GEOLOGY. 

of  many  pieces,  which  branched  out  into  numerous  tenta- 
cula  (<?)  for  the  purpose  of  seizing  its  prey.  The  whole 
animal  is  supposed  to  have  been  invested  with  a  gelatinous 
covering,  by  which  its  structure  was  held  together.  In  the 
skeleton  of  some  specimens,  not  less  than  2(i,000  bones, 
or  pieces  of  calcareous  matter,  have  been  counted,  all  beau- 
tifully marked,  and  ingeniously  adapted  to  each  other;  and 
in  a  framework  so  liable  to  be  broken,  we  find  traces  of  a 
power  to  reproduce  mutilated  parts,  such  as  we  find  in  the 
crabs  and  star-fishes  of  the  present  day.  Little  more  is 
known  of  the  structure  of  these  crinoidea,  or  of  the  habits 
and  peculiarities  of  the  different  genera.  The  seas  at  this 
period  seem  to  have  swarmed  with  them ;  their  remains 
are  found  in  every  stratum  of  a  calcareous  character,  and 
masses  of  limestone  from  40  to  120  feet  in  thickness  are 
almost  wholly  composed  of  them,  just  as  existing  coral-reefs 
are  formed  of  various  corals.  In  consequence  of  the  com- 
plex constitution  of  the  skeleton,  and  the  perishable  nature 
of  the  enveloping  membrane,  entire  specimens  are  seldom 
or  ever  found;  the  separate  pieces  having  been  drifted  and 
scattered  about  after  the  surrounding  cartilage  was  decom- 
posed. Fig.  B.  represents  a  fragment  of  mountain  or  en- 


Fig.  B Fragment  of  Encrinital  Limestone. 

61 1.  What  is  most  remarkable  in  their  structure  1 

512.  Wherein  do  they  resemble  crabs  and  star-fish  ? 

513.  In  what  state  are  they  usually  found  ? 
614.'  Describe  and  explain  the  ievera.  diagrams. 


MOUNTAIN,  OR  CARBONIFEROUS  LIMESTONE.  133 

crinital  limestone,  which,  when  sufficiently  hard,  furnished 
a  curious  and  highly  ornamental  marble. 

I8D.  Bt  sides  crinoidea,  ihe  mountain  limestone  contains 
many  othrr  species  of  radiuria — branched,  fungous-shaped, 
fan-shaped,  star-shaped,  and  tubular.  These  differ  in  many 
instances  from  the  corals  of  the  silurian,  as  they  differ  from 
those  of  the  present  day;  and  are  confusedly  mingled  with 
corallines,  shells,  teeth,  spines,  and  scales  of  fishes.  The 
following  engraving  represents  some  of  the  more  prevalent 
forms  among  the  corals  and  corallines  of  this  era  : — 


1.  Syringipora.  2.  Retepora.  3.  Cyathophyllum  basaltiforme. 
190.  The  shell-Jish  of  this  group  are  also  exceedingly 
numerous,  and  of  curious  and  gigantic  forms.  They  belong 
to  all  orders — equal  and  unequal  bivalves,  single  and  many- 
chambered  univalves;  many  of  them  are  not  to  be  f  und 
in  any  other  strata  than  those  of  the  carboniferous  era. 
Several  families  seem  (like  the-  oyster  and  cockle  of  the 
present  d  iv)  to  hnve  been  gregnrious,  covering  large  spaces 
of  the  ocean's  bed;  for  shells  are  found  composing  beds  of 
limestone  from  one  to  six  feet  in  thickness;  others  to  have 
been  solitary,  changing  their  places  as  necessity  required ; 
while  the  chambered  shells,  like  the  argonaut  and  nautilus, 
possessed  the  power  of  sinking  or  floating  at  pleasure. 
(See  par.  222.)  Like  existing  shell-fish,  they  appear  to 
have  inhabited  the  seas  at  moderate  depths  from  the  shores, 
and  to  have  preyed  partly  on  each  other,  and  partly  on 
marine  vegetables.  Their  numbers  and  size  indicate  a 

515.  What  variety  of  shell-fish? 

516.  What  proof  of  their  being  gr«  garious  ? 

517.  What  geological  reasoning  ia  hence  derived  ? 

518.  Explain  the  diagrims. 


14;)  GBOLOGY. 

genial  condition  of  the  ocean  both  as  regards  temperature 
and  calcareous  matter — the  former  fostering  their  growth 
with  rapidity,  and  the  latter  yielding  material  for  the  struc- 
ture of  their  shelly  coverings.  Some  of  the  more  typical 
shells  belonging  to  this  formation  are  the  Producta,  Tere- 
bratula,  Spinfera,  and  Inoceramus  among  the  bivalves; 
and  the  Euomphalus,  Ammonite,  Bellerophon,  Orthocera- 
tite,  and  Goniatite  among  the  univalves,  which  are  chiefly 
many-chambered. 


1.  Producta  scabriculus  ;    2.  Inoceramus  vetustus ;     3.  Bellerophon 
tangentialis  ;   4.  Orthoceras  cinctum. 

191.  Crustacea  nnd  Jishes  have  been  found  in  all  the 
•nembers  of  the  carboniferous  system,  from  the  lowest  beds 
of  the  mountain  limestone  to  the  highest  of  the  coal  mea- 
sures. The  crusfacea  are  chiefly  trilobites,  though  broken 
plates  of  other  genera  are  not  uncommon;  and  some  of 
the  calcareous  shales  yield  species  bearing  a  faint  analogy 
to  the  chiton  of  modern  seas.  The  trilobites  of  the  moun- 
tain limestone,  however,  are  less  numerous  and  varied  than 
those  of  the  silurian  era,  of  whose  Fauna  it  will  be  remem- 
bered they  formed  the  most  distinguishing  feature.  Irh- 
thyolites  are  exceedingly  numerous,  either  as  entire  fishes, 
detached  scales,  spines,  teeth,  or  coprolites.  The  fishes 
belong  for  the  most  part  to  the  Ganoid  order,  though  Pla- 
coidians  are  not  unfrequent.  Many  of  these  are  of  gigantic 
size,  such  as  the  megalichthys  (large  fish),  holoptychius, 
&c.  and  bear  so  much  analogy  to  reptiles  in  the  bones  of 
their  head  and  external  coverings,  as  to  induce  M.  Agassiz 
to  term  them  "  sauroid  fishes."  Their  pnlatal  bones,  spines, 

519.  What  of  the  Crustacea  ? 

520.  What  varietv  of  ichthyoiites  7 


COAL  MEA^t'RF*.  141 

and  teeth  are  found  in  abundance,  seme  of  the  latier  being 
more  than  four  inches  in  length — thereby  denoting  ihe 
gigantic  size  of  these  predatory  animals.  Their  coprolites 
(Gr.,  kopros,  dung,  and  lithos,  a  sione),  or  fossil  excre- 
ments, are  scattered  throughout  the  shales  and  calcareous 
strata,  and  attest,  by  the  fish-scales,  bones,  &c.  which  they 
contain,  the  nature  of  the  food  on  which  they  subsisted. 

COAL  MEASURES. 

192.  The  term  "Coal  Measures"  is  applied  to  that  series 
of  rocks  which  immediately  overlies  the  mountain  limestone, 
and  from  which  the  well-known  mineral,  coal,  is  obtained. 
The  group  is  composed  of  alternations  of  coals,  sandstones, 
shales,  bands  of  ironstone,  fire-clay,  and  layers  of  impure 
limestone.  The  coals  present  every  degree  of  fineness  and 
purity,  and  are  generally  distinguished  as  follows: — An- 
thracite, a  hard,  shining  variety,  destitute  of  bitumen,  often 
called  mineral  charcoal ;  caking,  a  highly  bituminous  sort, 
like  that  of  Newcastle,  which  cakes  or  runs  together  during 
combustion;  cubic,\ess  bituminous, breaking  up  into  cubi- 
cal masses ;  cannd,  a  compact  lustrous  variety,  which  breaks 
with  a  conchoidal  fracture;  jet,  still  more  compact  and 
lustrous;  and  lignite,  or  brown  coal,  in  which  the  woody 
structure  of  the  vegetables  is  still  perceptible.  The  sand- 
stones are  in  general  quartzose,  of  a  dull-white  or  brown 
colour,  and  thick-bedded ;  sometimes  they  are  flaggy,  or 
schistose,  and  in  this  instance  are  either  of  a  calcareous  or 
argillaceous  character.  The  shales  are  all  dark-coloured, 
and  bituminous;  the  fire-clays  grayish-white,  and  more  or 
less  sandy ;  the  ironstone  occurs  either  in  bands  or  nodules; 
and  the  limestones  are  all  earthy  and  impure.  The  iron- 
stone of  earlier  formations  occurs  either  in  veins,  or  is  dis- 
seminated as  colouring  matter  through  the  mass ;  in  this 
system  it  appears  as  an  argillaceous  carbonate,  either  in 
thin  layers  from  one  to  twelve  inches  thick,  in  irreguhu 

521.  What  of  their  sire,  and  means  of  subsistence  7 

522.  Define  and  explain  coal  measures. 

523.  Into  what  varieties  are  the  coals  distinguished  ? 

524.  With  what  other  minerals  are  they  associated  f 
535.  How.-  doe*  ironstone  occur  heret 

,7 


142  GEOLOGY. 

noddles,  or  in  bands  of  regular  nodules,  called  sf.ptaria, 
from  the  nodule  being  often  internally  divided  into  numer- 
ous septa,  or  partitions,  as  shown  in  4  of  the  following 
engraving.  These  nodules  seern  to  have  been  formed  by 
some  process  of  attraction  round  a  central  nucleus,  as  in 
nine  cases  out  of  ten  they  contain  nuclei  of  leaves,  teeth, 
scales,  or  spines  of  fishes,  coprolites,  or  some  other  organic 
matter.  Beneath  is  represented  as  central  nuclei — 1,  a 
fragment  of  a  plant;  2,  a  fish-tooth;  3,  fossil  excrement, 
or  coprolite;  and,  4,  true  septaria,  with  their  curious  parti- 
tions of  white  cirbonate  of  lime,  giving  the  section  the 
appearance  of  a  beetle;  from  which  circumstance  such 
nodules  are  known  in  some  places  as  beetle-stones. 


Ironstone  nolules,  showing  varieties  of  central  nuclei. 
li)3.  There  is  no  regular  suc.r.f.ssion  among  the  beds  of 
this  group;  though  it  rnav  be  remarked,  that  the  thickest 
and  best  seams  of  coal  abound  about  the  middle  of  the 
series.  Immediately  above  the  mountain  limestone  the 
coal  beds  are  thin,  the  shales  thick-bedded,  and  more  or 
less  calcareous ;  and  the  sandstones  often  calcareous  and 
argillaceous.  As  we  ascend,  the  argillaceous  and  calcare- 
ous members  become  less  prevalent,  the  coals  thicker  and 
mor?  frequent,  and  the  shales  more  bituminous.  Further 
up  in  the  series,  the  coals  gradually  disappear,  fire-olqys 
and  light-coloured  shales  abound,  the  sandstones  become 
more  purely  arenac°ous,  assume  various  shades  of  colour, 
and  insensibly  pass  into  the  superincumbent  new  red  sand- 
stone. In  general,  all  the  members  alternate  indiscrimi- 

526.  What  of  the  nuclei  of  these  nodules  ? 

527.  Explain  the  diagrams,  and  their  common  name  ? 

528.  What  of  the  succession  in  the  beds  of  this  strata  ? 

529.  What  is  the  relation  of  the  new  red  sandstone  1 


COAL  MEASURE*.  M3 

natrly  with  each  other,  present  various  degrees  of  fineness, 
colour,  and  mineral  composition,  and  are  persistent  over 
extensive  areas.  Occasionally,  a  stratum  will  thin  out  and 
disappear ;  at  other  times  it  will  part,  as  it  were,  into  two, 
with  a  layer  of  different  material  between;  yet,  notwith- 
standing such  anomalies,  there  is  no  series  of  strata  so 
regularly  deposited  as  the  coal  formation. 

11)4.  In  the  organic  remains  of  the  coal  mfatures,  the 
abundance  of  terrestrial  vegetation  is  by  far  the  most  dis- 
tinguishing feature  :  though,  as  might  be  expected  from  the 
nature  of  the  deposit,  marine  shells,  fishes,  and  other  aquatic 
exuviae  are  not  unfrequent.  It  has  been  already  stated  that 
coal  is  of  vegetable  origin  ;  in  other  words,  that  its  mass  is 
composed  of  plants  altered  by  compression  and  that  process 
of  bituminization  described  in  par.  115.  On  account  of 
this  change,  it  is  often  impossible,  at  first  sight,  to  detect 
any  trace  of  vegetable  structure;  but  on  closer  inspection, 
the  woody  fibre  may  be  seen  in  many  specimens;  while  it 
is  possible  in  almost  all  to  make  visible  the  cells  and  fibre 
by  exposing  thin  slices  to  the  transmission  of  a  powerful 
light.  In  this  way  Mr.  Witham  observed  the  various  vege- 
table tissues  in  coal,  thereby  adding  another  testimony  to 
the  numerous  evidences  of  its  organic  origin.  In  most  of 
the  bituminous  beds,  however,  the  external  form  is  oblite- 
rated, and  it  is  to  detached  fosstib  in  the  sandstones  and 
lighter  shales  that  the  geologist  is  i,.tiobted  for  his  know- 
ledge respecting  the  Flora  of  the  carboniferous  era.  About 
four  hundred  species  have  been  already  determined,  chiefly 
gigantic  equisetums,  ferns,  club-mosses,  cactuses,  pines,  and 
plants  allied  to  the  bulrush,  cane,  and  bamboo.  Most  of 
these  resemble  existing  plants  merely  in  their  generic  dis- 
tinctions, having  belonged  to  species  which  flourished 
during  the  coal-forming  period,  and  became  extinct  with 
the  peculiar  conditions  of  the  globe  which  gave  them  birth. 
Some  of  the  most  characteristic  of  the  vegetable  fossils  be- 

530.  What  fossil  remains  are  abundant  in  coal,  and  what  are  less 

frequent? 

531.  What  of  the  origin  of  coal,  and  how  formed? 

532.  How  is  its  organic  origin  made  visible  ? 

533.  What  of  the  species  of  plants  already  determined  ? 


144 


GEOLOGY. 


longing  to  this  formation  are  represented  beneath  ;  namely 
—  1.  Sigillaria,  so  called  from  the  graven  appearance  of 
its  stern;  2.  Calamitcs,  from  the  leed-like  jointings  of  its 
stalk;  3,  Stigmaria,  from  its  stigmata,  or  punctures;  4. 
Lepidodendron  (Gr.,  lepis,  a  scale,  and  dtndron,  a  tree), 
from  the  scaly  appearance  of  its  bark.  These  fossils  occur 


1.  Sigillaria  pachyderma  ;  2.  Calamites  cannaeformis  ;   3.  Stigmaria 
ficoides  ;  4.  Lepidodendron  Sternbergii. 

in  all  the  members,  from  the  lowest  white  sandstone  be- 
neath the  mountain  limestone,  up  to  the  commencement 
of  the  new  red  sandstone,  at  which  stage  they  disappear, 
and  do  not  seem  to  have  flourished  during  the  deposition 
of  any  subsequent  formation.  The  best  preserved  speci- 
mens are  found  in  the  shales  and  sandstones;  the  interior 
structure  of  the  plant  being  converted  into  soft  quartzose 
sandstone,  and  the  bark,  or  cuticle,  into  a  glistening  bitu- 
minous coal.  In  the  coal,  the  vegetable  structure  is  always 
more  or  less  obliterated,  though  sometimes  a  solitary  trunk 
occurs  of  the  same  quartzose  material  as  those  imbedded 
in  the  shales  and  sandstones.  Of  these  fossil  trees,  many 
have  been  found  of  gigantic  dimensions;  as,  for  example, 
a  lepidodendron  in  the  Jarrow  coal-field  13|  feet  wide  at  the 
base,  arid  39  feet  high^  exclusive  of  the  branches  at  the  top, 
which  were  also  entire;  and  a  conifera  of  the  genus  atira- 
caria  in  Craigleith  quarry,  3  feet  in  diameter,  and  20  feet 
long.  Besides  the  sigillaria,&c.  above  described,  there  are 

53-4.  Explain  the  diagrams. 

535.  Name  the  variety  in  locality  and  appearance. 

536.  Have  any  large  trees  been  found  in  the  coal  formation  1 


COM,  MF  AS  runs. 


145 


numerous  species  of  tree-ferns,  club-mosses,  equisetums, 
and  other  cryptogamic  plants  preserved  in  the  shales:  their 
dark  carbonaceous  leaves  and  branches  being  often  beau- 
tifully displayed  upon  the  light-coloured  ground  of  the  ma- 
terial in  which  they  are  imbedded.  Of  these  the  following 
engraving  exhibits  some  of  the  most  characteristic ;  namely, 
Aster ophyllites  (Gr.,  aster,  a  star,  and  phyllo/1,  a  leaf); 
Sphenopteris  (sphen,  a  wedge,  and  pttron,  a  wing) ;  Pecop- 
tt-.ris  (pekos,  a  comb,  and  pferon,  a  wing);  all  so  named 
from  the  shape  of  their  respective  leaves. 


Stem  an'd  leaves  of  Asterophyllites;  2.  Spheaopteris  Arcaris ;  3.  Pe- 
copteris  Mautelli ;  4.  Sphenopteris  affinis. 

195.  Of  the  conditions  of  the  world  during  the  deposition 
of  the  carboniferous  system,  we  have  more  obvious  evidence 
than  those  under  which  any  of  the  earlier  systems  were 
formed.  The  extent  of  the  seas  in  which  the  deposit  took 
place  is  very  clearly  indicated  by  the  course  of  the  moun- 
tain limestone,  which  must  have  been  formed  at  no  great 
depths  from  the  shore,  as  its  corallines,  corals,  shells,  and 
other  exuviae,  prove  it  to  be  of  littoral  origin.  All  the 
members  of  the  system,  with  the  exception  perhaps  of  the 
limestones,  are  eminently  sedimentary ;  and  the  numerous 
alternations  of  these  strata  evince  frequent  changes  in  the 
depositing  agents.  At  one  time  the  rivers  seem  to  have 

537.  Explain  the  diagrams. 

538    What  of  the  geological  indicitions  here  ? 

539.  What  of  the  sedimentary  deposits  from  rivers  I 


14(5  GEOLOGY. 

carried  down  sand  to  form  sandstones,  at  another  clay  and 
mud  lo  form  shale,  arid  at  a  third  period  vegetable  drift  to 
form  coal ;  for  strata  of  these  materials  often  directly  over- 
lie each  other.  It  must  be  borne  in  mind,  however,  that 
sand,  clay,  and  plants,  might  be  carried  down  at  the  same 
time,  and  that  they  would  arrange  themselves  according  to 
their  gravity — the  sand  depositing  itself  along  the  shores, 
the  mud  farther  seaward,  and  the  vegetables  in  any  still  bay 
where  currents  of  wind  or  water  might  drift  them.  Such 
an  arrangement  would  take  pface  under  the  ordinary  opera- 
tions of  water ;  but  during  violent  inundations,  there  would 
be  a  confused  intermingling  of  sand,  mud,  and  plants,  and 
this  we  often  discover;  so  that,  taking  all  things  inlo  account, 
we  learn  that  the  same  agencies  of  rivers,  waves,  and  tides, 
existed  during  the  deposition  of  the  carboniferous  rocks  as 
exist  at  the  present  day,  only  on  a  more  gigantic  and  uni- 
form scale.  Looking  at  the  abundance  of  marine  life  which 
must  have  thronged  the  waters  during  the  formation  of  the 
mountain  limestone,  and  at  the  vast  amount  of  vegetation 
which  the  earth  must  have  sustained  while  the  deposition 
of  the  coal  measures  took  place,  we  are  led  to  infer  that  the 
earth  then  enjoyed  a  much  higher  and  more  uniform  tem- 
perature than  it  has  ever  since  experienced.  At  present, 
we  find  a  faint  analogy  in  the  Fauna  of  the  tropical  seas, 
and  in  the  Flora  of  the  tropical  jungles,  to  those  of  the 
carboniferous  era ;  but  so  faint,  that  we  can  scarcely  insti- 
tute a  comparison  between  the  results  produced.  The 
coral-reefs  of  the  Pacific  are  insignificant  compared  with 
the  thickness  and  extent  of  the  mountain  limestone;  and 
the  vegetable  drift  of  the  Mississippi  and  Ganges  combined, 
would  scarcely  produce  carbonaceous  matter  sufficient  to 
colour  one  stratum  of  shale.  Notwithstanding  this,  there 
is  a  resemblance  between  the  coral  productions  of  the 
Pacific  and  those  of  the  mountain  limestone;  and  between 
the  palms,  tree-ferns,  canes,  and  cactacea3  of  the  tropics, 
and  the  fossil  plants  of  the  coal  measures.  The  heat  of  the 
tropics  is  directly  derived  from  (he  sun,  and  the  torrid  zone 

540.  What  inference  is  drawn  touching  the  ancient  earth  ? 

541.  How  is  a  higher  and  more  uniform  temperature  inferred  ? 


COAL  MEASURES.  147 

occupies  but  a  narrow  belt  of  the  earth's  surface ;  whereas 
the  coal  measures  are  to  be  found  almost  in  every  region 
of  the  globe.  The  sun  could  not,  therefore,  have  yielded 
that  temperature  which  nourished  the  plants  and  animals 
of  this  period ;  for  though  the  sun's  heat  had  been  greater 
than  at  present,  it  could  not  have  been  universally  diffused. 
The  conclusion,  therefore,  to  which  most  geologists  have 
come,  is,  that  the  earth,  originally  an  incandescent  mass, 
was  gradually  cooled  down — hot  enough  to  render  gneiss 
and  mica  schist  crystalline;  cool  enough  during  the  grau- 
wacke  and  silurian  eras  to  permit  of  marine  corals,  shell- 
fish, and  Crustacea  ;  cooler  still  during  the  life  of  the  plated 
fishes  of  the  old  red  sandstone  ;  and  only  sufficiently  genial 
throughout  the  deposition  of  the  carboniferous  period  to 
foster  a  growth  of  terrestrial  vegetation  all  over  its  surface, 
to  which  the  existing  jungles  of  the  tropics  are  mere  bar- 
renness in  comparison.  This  hi'gh  and  uniform  tempera- 
ture, combined  (as  suggested  by  Brogniart)  with  a  greater 
proportion  of  carbonic  acid  gas  in  the  atmosphere,  would 
not  only  sustain  a  gigantic  and  prolific  Flora,  but  would 
also  create  denser  vapours,  showers,  and  rains;  and  these, 
again,  gigantic  rivers,  periodical  inundations,  and  deltas. 
Thus  all  the  conditions  for  extensive  estuary  deposits  would 
arise  from  this  high  temperature;  and  every  circumstance 
connected  with  the  coal  measures  points  to  such  conditions. 
IU6.  With  regard  to  the  formation  of  coal,  geologists 
are  not  yet  fully  agreed.  On  examining  sandstone  or  shale, 
it  is  easy  to  perceive  from  their  structure,  texture,  and  com- 
position, that  they  must  at  one  time  have  been  respectively 
loose  sand  and  mud,  borne  down  and  deposited  by  water ; 
but  the  case  is  somewhat  different  with  beds  of  coal.  This 
mineral,  being  chiefly  composed  of  carbon,  hydrogen,  and 
oxygen — the  same  elements  which  enter  into  the  composi- 
tion of  plants — and  revealing  in  its  mass  evidence  of  vege- 
table structure,  no  doubt  is  entertained  of  its  organic  origin. 
But  whether  the  plants  of  which  it  is  composed  were 

642    Wny  is  it  argued  that  the  sun  could  not  furnish  heat  enough  1 
643.  Whence  is  it  supposed  that  the  necessary  heat  was  derived  T 

544.  What  geological  leasoning  is  here  adopted  ? 

545.  Of  what  chemical  elements  is  coal  chiefly  composed? 


148  GEOLOOY. 

drifted  down  by  rivers  and  deposited  along  with  layers  of 
rnud  and  sand  in  estuaries,  or  whether  dense  forests  and 
peat-mosses  were  submerged,  and  then  overlaid  by  deposits 
of  sand  and  mud,  are  the  questions  at  issue.  According  to 
the  latter  hypothesis,  the  vegetable  matter  must  have  grown 
in  dense  jungles  for  many  years;  then  the  land  must  have 
sunk,  and  become  the  basin  of  a  lake  or  estuary,  in  which 
situation  rivers  would  wash  into  it  rnud  and  sand,  and  these 
would  cover  the  vegetable  mass,  and  form  beds  of  shale  and 
sandstone.  This  being  done,  it  is  supposed  that  the  area 
of  deposit  was  again  elevated,  so  as  to  become  the  scene  of 
luxuriant  vegetation ;  again  submerged,  and  overlaid  by 
new  deposits  of  sandstone  and  shale ;  once  more  elevated, 
and  covered  with  plants,  and  then  submerged ;  and  this 
alternating  process  of  submergence  and  elevation  is  con- 
tended to  have  taken  place  as  often  as  there  are  beds  of 
coal  in  any  particular  coal-field.  The  other  theory  is,  that 
while  partial  elevations  and  submersions  might  take  place 
as  at  the  present  day,  the  great  mass  of  the  coal  measures 
was  deposited  in  lakes  arid  estuaries;  that  the  vegetable 
matter  of  which  coal  is  formed  was  drifted  into  these  estu- 
aries by  rivers  and  inundations;  and  that  various  rivers 
might  discharge  themselves  into  one  estuary,  some  chiefly 
carrying  down  sand,  while  others  transported  plants,  mud, 
and  heterogeneous  debris.  This  theory  also  supposes  that 
the  transporting  rivers  were  subject  to  periodical  inunda- 
tions, and  that,  during  the  intervals  of  overflow,  the  deltas 
were  choked  with  a  rank  vegetation,  which,  in  conjunction 
with  the  vegetable  drift  from  inland,  went  to  the  formation 
of  beds  of  coal. 

]  97.  Both  theories  are  at  present  beset  with  many  diffi- 
culties; but  the  latter  is  the  more  generally  received,  as 
accounting  for  most  of  the  phenomena  connected  with 
our  coal-fields.  According  to  the  former  theory,  a  sub- 
mergence and  elevation  must  have  taken  place  for  every 
seam  of  coal ;  and  as  in  some  districts  from  thirty  to  forty 


546.  What  are  the  questions  in  dispute  among  geologists  1 

547.  Name  the  two  theories  and  their  differences. 

548.  Name  some  of  the  objections  to  the  first  theory. 


COAL  MEASURES.  149 

seams  occur,  varying  in  thickness  from  a  few  inches  to 
many  feet,  it  is  impossible  to  conceive  how  the  earth,  in 
this  unstable  condition,  could  have  nourished  such  a  prolific 
Flora  as  the  coal  measures  clearly  demonstrate.  It  is  also 
justly  objected  against  this  theory,  that  some  thick  beds  of 
coal  are  subdivided  by  thin  layers  of  sandstone,  or  fer- 
ruginous shale,  a  fact  which  would  imply  that  many  eleva- 
tions and  submergences  took  place  even  during  the  forma- 
tion of  a  single  coal  bed ;  whereas  by  the  latter  theory, 
those  layers  of  sandstone,  &c.  present  no  difficulty,  as  the 
river,  while  it  bore  down  vegetable  drift,  would  carry  at  the 
same  time  sand  and  other  debris.  Further,  shells  and  fishes 
are  sometimes  found  imbedded  in  coal ;  and  it  is  difficult 
to  conceive  how  these  could  have  got  there,  unless  in  the 
ordinary  way  of  deposit  and  sediment.  Forests  of  coniferae, 
palms,  and  tree-ferns,  could  not  have  been  submerged  and 
covered  up  with  sand  and  mud,  without  the  trunks  being 
abundantly  found  in  an  upright  position;  now, this  upright 
position  of  fossil  trees  is  rarely  or  ever  met  with.  Again, 
had  coal  resulted  from  submerged  peat-mosses,  instead  of 
from  growing  forests,  there  is  no  means  by  which  we  can 
account  for  the  occurrence  of  shells,  fishes,  and  thin  layers 
of  sandstone  in  its  mass.  By  the  latter  theory,  all  these 
can  be  readily  accounted  for.  Over  vast  deltas,  such  as 
those  in  which  it  supposes  the  coal  measures  to  have  been 
deposited,  there  would  not  only  occur  growing  stems  of 
palms,  f«  rns,  reeds,  and  the  like,  to  be  silted  up  perpen- 
dicularly, but  there  would  also  occur  morasses  choked 
up  with  a  rank  growth  of  grasses,  while  in  the  creeks  and 
Ingoons,  shell-fish,  fishes,  and  other  aquatic  life  would 
abound.  In  the  deltas  of  existing  rivers,  the  latter  theory 
meets  with  a  perfect  analogy;  and  when  the  student  is  told 
of  the  rafts  of  the  Mississippi,  the  mangrove  jungles  of  the 
Niger,  and  the  sand  and  mud-banks  of  the  Ganges  (par. 
27VJ,  ^O,  &/c),  he  can  have  little  difficulty  in  forming  a 
conception  of  the  estuaries  in  which  the  sandstones,  shales, 
shell  limestones,  and  coal  of  the  carboniferous  era  were 
deposited. 


649.  Why  is  the  latter  theory  rendered  probable  T 


150  GEOLOGY. 

198.  The  i ff neons  rocks  assuciatfd.  with  tlic.  carboniferous 
system  are  all  of  the  trap  family — greenstones,  clinkstones, 
basalts,  trap-mils,  &c.     They  are  principally  composed  of 
felspar  and  hornblende,  with  admixtures  of  clay,  augite, 
and  occasionally  hypersthene.     The  greenstones  (vulgarly, 
whinstones)  occur  in  large  indeterminate  or  tabular  masses, 
arid  are  often  hypersthenic;  the  clinkstones  differ  little  from 
the  greenstones  in  mineral  composition,  but  are  more  com- 
pact, split  up  into  thin  schistose-like  fragments,  and  yield  a 
metallic  sound  when  struck  by  the  hammer;  the  basalts 
are  easily  known  by  the  columnar  structure,  their  dark  and 
compact  aspect,  and  from  their  containing  little  spherical 
crystals  of  a  greenish  mineral  called  olivine;  and  the  trap' 
tuffs  are  of  all  varieties,  from  a  soft   scoriaceous-looking 
mass  to  a  confused  conglomerate  of  fragments  of  basalt, 
greenstone,  sedimentary  rocks,  &c.     [Some  of  the  most 
interesting  scenery  in  this  country  is  formed  by  greenstone 
columns,  standing  upright,  or  leaning  only  a  few  degrees. 
The  Palisadoes,  on  the  Hudson  river,  a  few  miles  above 
New  York,  are  an  example.     But  in  Oregon,  where  the 
Columbia  river  passes  through  mountains  of  trap,  and  pro- 
bably basalt,  from  400  to  1000  feet  in  height,  a  vastly  more 
extensive  formation  of  this  kind  exists.]     The  trap  rocks 
of  the  carboniferous  era  are  easily  distinguishable  from  those 
of  any  other,  partly  by  their  darker  colour,  and  from  the 
fact  of  their  yielding  more  or  less  bitumen  by  distillation  ; 
and  partly  from  the  prevalence  of  basalts,  and  of  trap-tufts 
containing  fragments  of  limestone,  sandstone,  and  shale. 
Among  the  traps  of  the  old  red  sandstone,  felspar,  por- 
phyries, and  amygdaloids  prevail,  but  are  rarely  to-be  met 
with  among  those  of  the   coal    measures;   while,  on   the 
other    hand,  the  traps  associated   with  the   tertiary  strata 
assume  a  lighter  cotour,  and  a  decidedly  scoriaceous  and 
lava-like  aspect. 

199.  The  positions  of  the  carboniferous  trap  rocks  are 

550.  Of  what  family  are  the  igneous  rocks  of  this  system  1 

551.  Of  what  minerals  are  they  chiefly  composed  ? 
562.  Define  and  explain  the  italicised  terms. 

553.  How  are  the  trap  rocks  of  this  system  distinguished  ? 

554.  What  of  their  positions  T    ' 


COAL  MEASURES.  151 

either  disrupting,  overlying,  or  interstratified.  They  disrupt 
and  elevate,  as  in  the  mountain  limestone  hills,  and  in  the 
rounded  heights  and  isolated  irregular  cones  of  the  coal 
measures.  Basalt,  or  greenstone,  sometimes  overlie,  as  if 
poured  in  a  state  of  liquid  lava  over  the  subjacent  strata ; 
and  trap-tuffs  also  overlie,  from  their  evidently  having  been 
strown  abroad  in  the  form  of  volcanic  dust  and  ashes.  The 
trap  rocks  of  this  era  more  frequently  assume  the  in terst ra- 
tified form  than  those  of  any  other  formation;  apparently 
irom  the  fiict,  that  volcanic  discharges  took  place  in  the  seas 
and  estuaries  in  which  the  coal  measures  were  being  depo- 
sited— these  discharges,  whether  in  the  form  of  lava  or  ashes, 
being  overlaid  by  subsequent  deposits  of  sedimentary  matter. 
2'JO.  The  structure  and  texture  of  these  igneous  rocks 
differ  as  widely  from  the  granitic  series  beneath  as  from  the 
volcanic  above.  They  are  generally  close-grained,  and  less 
distinctly  crystalline  tharr  the  former,  and  more  compact 
and  less  vesicular  than  the  latter.  The  structure  of  the 
tuffs  and  porphyries  is  massive  and  indeterminate;  of  the 
greenstones  sometimes  massive,  but  generally  tabular  or 
cuboidal;  and  of  the  basalts  always  columnar.  This  differ- 
ence in  the  structure  and  texture  of  these  rocks  seems  to 
have  arisen  not  so  much  from  any  difference  in  their  min- 
eral composition,  as  from  the  circumstances  attending 
their  cooling.  This  has  been  satisfactorily  proved  by  the 
experiments  of  Sir  James  Hall  and  Mr.  Gregory  Watt,  who, 
by  fusing  various  kinds  of  trap,  produced,  by  different 
modes  of  cooling,  not  only  columnar  basalt,  but  spherical 
greenstone  and  vesicular  tufa.  The  same  substance  which, 
when  suddenly  cooled,  forms  a  black  glass  or  obsidian,  will, 
by  a  slower  process  of  rerrigeration,  ibrm  basalt,  or  by  a 
still  slower,  pass  into  earthy  tufi.  By  gradually  cooling 
the  fused  mass,  columnar  basalt  may  be  formed;  but  if  at 
a  certain  stage  of  the  process,  it  be  rapidly  cooled,  spheri- 
cal masses  will  be  produced,  which,  when  exposed  to  the 
weather,  exfoliate,  or  decompose  coating  after  coating. 
l$y  these  experiments,  it  was  also  proved  that  the  primary 

555  How  are  volcanic  dischaiges  proven  to  have  taken  place  7 

556  What  of  their  structure  and  texture  T 

557.  Ho.v  is  this  shown  to  have  been  dependent  AH  cooling? 


152 


GEOLOGY. 


form  or  crystal  into  which  volcanic  rock  arranges  itself 
when  cooled,  is  spherical;  and  by  these  spheres  pressing 


StafFa — Fingal's  Cave. 

upon  each  other,  are  produced  tabular,  cuboidal,  and  colum- 
nar forms.  This  fact  can  be  readily  illustrated  by  putting 
a  number  of  spherical  pellets  (of  putty  or  any  other  yielding 
material)  into  a  vessel,  and  then  gently  pressing  upon  them, 
when  they  will  be  seen  to  arrange  themselves  in  five  and 
six-sided  columns,  precisely  similar  to  the  five  and  six- 
sided  columns  of  Staffa,  or  the  Giant's  Causeway. 

20 1 .  The  fffcct  of  igneous  forces  upon  the  coal  measures 
has  been  to  throw  them  into  troughs  and  basins,  to  elevate 
and  depress  them  in  a  very  extraordinary  manner.  The 


e   g 


c  c 

Trough  or  Basin  Form  of  Coal-fields. 


558.  What  of  the  primary  form  or  crystal  of  volcanic  rock  T 

559.  What  varieties  result  from  this  spherical  form  ? 

560.  How  may  we  illustrate  this  by  experiment  ? 

561.  Whnt  obvious  effect  of  igneous  forces  is  named? 

562.  Expl-rn  the  firnt  diagram. 


COAL  MEASURFS. 


153 


foregoing  engraving  represents  a  section  of  the  South  Glou- 
cestershire coal-field  (omitting  faults),  and  may  be  taken  as 
the  type  of  the  trough  or  basin.  Here  a  is  the  elevatory 
axis  of  the  Mendip  hills,  overlaid  by  the  old  red  sandstone 
d;  b  b  are  strata  of  carboniferous  limestone  resting  at  a 
high  inclination  upon  the  slopes  of  the  hills,  and  reappear- 
ing at/;  c  c  and  the  other  darkened  layers  are  beds  of  coal; 
tee  denote  the  new  red  sandstone  lying  unconformably 
upon  the  coal  measures;  gg  detached  outliers  of  lias;  and 
h  is  a  detached  outlier  of  inferior  oolite,  which  are  respec- 
tively continued  in  i  and  k;  I  is  the  upper  oolite,  and  m  m 
are  beds  of  Oxford  clay  situated  to  the  north  of  the  town  of 
Malmesbury.  The  upthrows  and  downthrows  of  the  coal 
strata  which  have  taken  place  in  consequence  of  irregular 
upheavings  and  sinkings  among  the  masses  on  which  they 
rest,  are  repre- 
sented in  the 
subjoined  figure. 
Here  the  faults 
or  slips  d  d  d, 
and  the  dyke  e, 
are  respectively 
accompanied  not 
only  by  an  up- 
throw or  down- 
throw, but  also  by  a  different  inclination  of  the  strata.  This 
mode  of  fracture  is  of  frequent  occurrence  in  every  known 
coal-field,  showing  in  a  striking  manner  the  nature  of  the 
agitations  which  have  taken  place  below.  In  the  vale  of 
the  Esk,  in  Mid-Lothian,  which  does  not  measure  more 
than  ten  miles  each  way,  the  coal-field  shows  120  ascer- 
tained dislocations,  one  of  which,  at  Sheriffhall,  throws 
down  the  strata  five  hundred  feet.  In  the  Newcastle  coal- 
field, there  is  a  famous  slip  called  the  ninety-fathom  hitch, 
the  deviation  from  the  line  of  stratification  being  no  less 
than  450  feet.  The  coal-fields  of  Fife  and  Clackmannan 
abound  in  such  dislocations,  several  of  them  throwing  the 

563.  What  of  the  next  diagram  ? 

564.  What  is  the  geological  reasoning  here  ? 

565.  Name  instances  of  remarkable  dislocations  of  strata. 


Dislocations  of  Coal  Strata. 


154  GEOLOGY. 

strata  from  400  to  1200  feet  up  or  down,  as  the  case  may 
be,  from  the  general  position. 

202.  The  extent  of  country  occupied  by  the  carboniferous 
system  is  not  great,  the  deposit  being  found  only  in  limited 
and  detached  areas.    It  occurs  largely  in  the  British  islands, 
and  to  this  circumstance  is  mainly  owing  our  greatness  as 
a  nation — the  formation  being  rich  in  co*al,  iron,  and  lime — 
three  of  the  most  essential  minerals  to  civilized  existence. 
It  presents  itself  in  the  Lowlands  of  Scotland,  in  the  nor- 
thern and  middle  districts  of  England,  in  Wales,  and  in 
Ireland  ;  it  occurs  also  in  some  districts  of  Spain,  in  central 
France,  Germany,  and  in  Middle  Europe;  in  Hindostan,  in 
Australia,  and  New  Zealand;  in  the  island  of  Batavia,  and 
on  the  eastern  coast  of  China;  in  Melville  island;  in  Nova 
Scotia,  and  in  the  States  of  North  America,  especially  in 
Pennsylvania. 

203.  The  physical  aspect   of  carboniferous  districts   is 
rather   tame   and   unprepossessing.     The  hills  connected 
with  tbe  mountain  limestones  sometimes  present  considera 
ble  variety  of  scenery,  owing  to  the  bold  escarpments  of 
that  rock,  its  extensive  fissures  and  caverns,  and  the  irregu 
lar  undulations  of  the  trap.     These  features  are  also  aided 
by  the  general  verdure  and  fertility  of  limestone  districts, 
which  present  a  freshness  and  luxuriance  peculiar  to  them- 
selves.     The  coal  districts  are  almost  always  tame  and 
unattractive,  relieved  by  few  elevations  or  depressions  of 
picturesque  beauty,  and  being,  in  general,  bleak  and  unfer- 
tile from  the  cold  and  retentive  nature  of  the  soil.   Occa 
sionally,  a   basaltic  crag  or  isolated   trap-hill  relieves  the 
monotony;  but  this  is  the  exception  to  the  general  rule. 

204.  The  economical  value  of  the  carboniferous  system 
fully  compensates  for  any  deficiency  in  the  fertility  of  its 
soil,  or  in  the  picturesque  beauty  of  its  geographical  fea- 
tures.    Building-stone  of  the  finest  quality  (of  which  that 
of  Craigleith,  near  Edinburgh,  and  of  Calelo  in  Fife,  are 
good  examples)  are  obtained  from  the  sandstones  beneath 
the  mountain  limestone;  while  the  millstone  grit  and  flaggy 

566.  What  of  the  extent  of  the  carboniferous  system  ? 

567.  What  of  the  physical  geography? 

568.  What  of  tf  t  economical  value  of  this  system  ? 


COAL  MEASURES.  155 

beds  of  the  coal  measures  yield  other  valuable  freestones. 
Of  all  the  limestones  in  the  crust  of  the  earth,  the  Mountain 
is  that  which  is  most  valuable  and  abundant;  and  from  it 
sre  principally  derived  those  stores  of  lime  so  indispensable 
10  the  purposes  of  the  builder,  agriculturist,  iron-founder, 
&c.  Where  the  encrinal  beds  are  sufficiently  hard  and 
crystalline,  they  furnish  a  very  prettily-marked  marble;  the 
joints,  stalks,  plates,  and  star-like  tubes  of  the  corals  shin- 
ing out  from  the  darker  matrix  in  which  they  are  imbedded. 
Many  ornamental  spars  (Derbyshire  spar)  are  found  in  the 
veins  of  the  mountain  limestone,  which  are  also  the  princi- 
pal sources  of  lead  ore  in  the  British  islands ;  Derbyshire, 
Alston  Moor  in  Cumberland,  and  Lead  Hills  in  Lanark- 
shire, being  well-known  lead-mining  districts.  Silver  and 
gold  are  both  more  or  less  associated  with  the  ores  of 
lead,  especially  the  former;  but  they  are  seldom  sought, 
after,  unless  in  connexion  with  lead.  Fire-clay  is  dug  up 
from  the  coal  measures  for  the  making  of  fire-bricks,  fur- 
nace linings,  &c.;  ochre  (hydrated  oxide  of  iron),  which 
occurs  in  several  coal-fields,  is  extensively  used  as  a  pig- 
ment:  and  alum  (sulphate  of  alumina)  is  obtained  from 
many  of  the  pyritous  shales  of  Germany.  Ironstone,  which 
is  found  in  the  coal-shales  either  in  bands,  nodules,  or 
septaria,ls  one  of  the  most  valuable  products  of  the  carbon- 
iferous system.  It  is  obtained  in  great  abundance,  and 
being  easily  reduced  to  a  metallic  iorm  by  the  application 
of  coal  and  lime,  in  which  the  system  abounds,  it  may  be 
said  to  form  one  of  the  prime  elements  of  any  country's 
mechanical  and  commercial  greatness.  About  two  millions 
of  tons  are  annually  manufactured  in  Britain  for  the  fabri- 
cation of  the  innumerable  machines,  utensils,  and  imple- 
ments to  which  cast-iron,  malleable-iron,  and  steel,  are 
respectively  applied.  But  notwithstanding  the  great  value 
of  these  rocks  and  metals,  they  do  not  equal  in  importance 
those  strata  of  coal,  which  form  the  main  distinguishing 
feature  of  the  system.  The  varieties  principally  used  in 

569.  What  metals  have  been  found  in  this  system  T 
670.  What  earths  are  obtained  thence  ? 

571.  What  of  the  value  of  the  ironstone  ? 

572.  N'tne  the  varieties  of  coal. 


156  GEOLOGY. 

Britain  are  caking,  splint,  cubic,  and  cannel  coal ;  anthra- 
cite is  that  mainly  employed  in  the  United  States;  lignite 
and  brown  coal  in  Germany;  and  jet  wherever  it  can  be 
obtained,  for  the  manufacture  of  ornaments.  Coal,  of  which 
we  have  historical  notice  so  early  as  the  beginning  of  the 
twelfth  century,  is  justly  regarded  as  the  main  support  of 
the  whole  system  of  British  production  ;  it  fuses  the  metals, 
produces  steam  which  sets  machinery  in  motion,  yields  gas 
for  light,  heats  our  apartments,  prepares  our  ibod,  and,  in 
short,  renders  all  the  resources  of  nature  fit  for  civilized 
use.  The  annual  consumption  of  coal  in  the  British  em- 
pire is  estimated  at  about  thirty  millions  of  tons;  and  the 
export  at  from  three  to  four  millions.  At  this  rate  of  con- 
sumption, fears  have  been  entertained  that  our  coal-fields 
would  speedily  be  exhausted ;  and  these  fears,  considering 
that  the  deposit  is  limited,  are  not  altogether  without  foun- 
dation. However,  calculating  the  amount  of  unwrought 
coal  in  South  Wales,  in  the  middle  and  northern  districts 
of  England,  and  in  the  Lowlands  of  Scotland,  and  making 
allowance  for  more  perfect  systems  of  mining,  and  more 
economical  modes  of  burning,  it  is  estimated  that,  at  the 
present  rate  of  consumption,  there  is  coal  sufficient  to  meet 
the  demand  for  2000  years. 

EXPLANATORY  NOTE. 

CARBONIFEROUS  (Lat.,  carbo,  coal,  and  fero,  I  bear) — coal-bearing  or 
coal-yielding ;  applied  to  that  system  of  strata  from  which  the  chief 
supplies  of  coal  are  obtained. 

SUB-CRYSTALLINE — less  than  crystalline,  or  not  distinctly  crystallized. 
In  geology,  the  prefix  sub  is  often  used  in  this  sense  ;  thus  we  say 
columnar  basalt,  when  the  columns  are  distinct  and  regular  in  shape, 
and  sub-  columnar ,  when  the  mass  presents  traces  of  an  irregular 
columnar  structure. 

ENCRINITES — In  many  instances,  the  calcareous  matter  of  the  en- 
crinite  has  been  dissolved,  so  as  to  leave  a  screw-like  cast  of  the  imper- 
foration  and  jointings.  These  casts  are  known  by  the  vernacular 
names  of  screw-stones  and  pulley-stones;  just  as  turbinoliae  (fig.  2,  p. 
116)  are  called  by  quarrymen  pipe-heads,  and  the  smaller  stalks  of  en- 
crinites  pipe-shanks  or  tubes.  Separate  pieces  of  the  stalks  are  known 

673.  To  what  important  uses  is  coal  adapted  ? 

574.  What  of  the  consumption  of  coal? 

575    What  of  the  extent  of  supply  ? 

576.  Define  and  explain  the  several  terms  in  the  note. 


COAL  MEASURES.  157 

in  the  north  of  England  as  St.  CvthberPs  beads,  from  a  legend  alluded 
to  by  Sir  Walter  Scott  in  the  following  lines : — 

On  a  rock,  by  Lindisfarne, 

St.  Cuthbert  sits,  and  toils  to  frame 

The  sea-born  beads  which  bear  his  name. 

From  the  wheel-like  shape  of  the  pieces  which  compose  the  stem  of 
the  encrinite,  they  are  sometimes  technically  termed  entrochi  (trochus, 
a  wheel),  and  the  limestone  through  which  they  are  scattered  entrochal 
limestone.  This  term,  however,  is  principally  applied  to  the  pieces  of 
the  minutest  stems. 

LIMESTONE  CAVERNS. — Caves  and  fissures  present  themselves  in  all 
rocks  which  have  been  subjected  to  the  influence  of  subterranean 
movements,  or  to  the  eroding  power  of  water ;  and  may  thus  occur 
either  in  igneous  rock,  as  Fingal's  Cave  in  Staifa,  or  in  sandstone,  as 
the  caverns  of  Arbroath.  It  is,  however,  in  limestone  that  the  most 
celebrated  caves  and  grottos  are  to  be  found ;  indiscriminately  in  the 
mountain,  magnesian,  or  oolitic  beds,  but  on  a  scale  of  far  greater 
splendour  and  magnificence  in  the  former.  Those  of  Derbyshire, 
Mitchelston  in  Ireland,  Paros  and  Antiparos  in  the  Archipelago,  Aus- 
tralia, &c.  are  examples  of  this  class,  and  have  been  formed  partly 
from  fissures  caused  by  igneous  movements,  and  partly  by  the  eroding 
influence  of  springs  and  subterranean  streams.  The  joints  and  divi- 
sional planes  which  so  numerously  intersect  the  mountain  limestone, 
no  doubt  greatly  facilitate  these  excavating  operations. 

ANTHRACITE  (Gr.,  anthrax,  coal) — a  variety  of  coal  almost  wholly 
deprived  of  its  bitumen.  It  may  be  regarded  as  a  natural  charcoal 
formed  by  subterranean  or  by  chemical  heat.  Common  bituminous 
coal  is  often  found  converted  into  anthracite  by  effusions  of  igneous 
rock ;  and  this  fact  suggests  the  idea  that  all  deposits  of  the  kind  have 
been  similarly  produced.  The  most  extensive  fields  of  anthracite  are 
in  Pennsylvania  and  the  bordering  states  of  North  America. 

BITUMENS  or  THE  CARBONIFEROUS  SYSTEM. — Besides  the  many  varie- 
ties of  coal,  which  are  bitumens  mingled  more  or  less  with  earthy 
impurities,  there  are  other  bituminous  substances  derived  from  the 
system.  Naphtha,  petroleum,  mineral  pitch,  and  asphalte,  ooze  out  by 
rents  ;  mineral  caoutchouc  (elaterite,  or  elastic  mineral  pitch)  is  found 
in  crevices  of  the  limestone  ;  and  a  number  of  mineral  resins  and  fats 
— such  as  common  mineral  resin,  sphero-resinite  (globular  drops  of 
mineral  resin),  mellite  (crystallized  resin  or  honeystone),  Hatchetine, 
(mineral  tallow),  &c. — are  obtained  in  small  quantities.  Carburetted 
hydrogen  (fire-damp)  and  carbonic  acid  gas  (choke-damp),  both  so  fatal 
to  miners,  seem  to  be  evolved  from  the  coal  beds  after  the  same  man- 
ner as  several  of  the  above-named  products. 

COPROLITES  (petrified  excrements)  are  found  in  all  the  systems  of 
the  secondary  and  tertiary  epochs.  They  are  chiefly  the  voidings  of 
fishes  and  sauroid  animals,  and  yield  unequivocal  evidences  of  their 
origin  in  containing  scales,  bones,  and  other  fragments  of  the  creatures 
on  which  these  voracious  animals  preyed.  Many  specimens  of  copro- 
lite  retain  on  their  external  surfaces  the  convolutions  and  corrugations 


577.  Define  the  terms  used  in  the  note. 


158  GEOLOGY. 

of  the  intestines;  and  masses  of  it  have  been  found  in  situ  within  the 
ribs  of  ichthyosauri. 

NEW  RED  SANDSTONE  SYSTEM. 

205.  After  the  deposition  and  upheaval  of  the  carbonifer- 
ous system,  a  new  era  occurs  in  the  history  of  the  globe. 
Overlying  the  coal  measures  in  some  places  conformably, 
and  in  others  not,  there  appears  a  set  of  red  sandstones, 
variegated   (yellow,  purple,   and   greenish)   shales,   thick- 
bedded   magnesian  limestones  of  a  cream  colour — all  of 
which  present  an  aspect  not  to  be  mistaken  for  any  previ- 
ous system  of  strata.     As  to  their  organic  remains:   there 
are   a  few  species  of  marine  zoophytes,  shells,  and  fishes, 
but  scarcely  a  trace  of  vegetation,  showing  that  the  condi- 
tions which  gave  birth  to  the  exuberance  of  terrestrial  plants 
during  the  coal  era  had  undergone  an  extensive  and  pecu- 
liar  change.     To  these  red  sandstones,  magnesian  lime- 
stones, arid  mottled  shales,  the  term  New  Red  Sandstone 
System  has  been  applied,  in  contradistinction  to  the  Old 
Red  which   underlie  the   carboniferous   strata ;    and    this 
term  we  adopt  in  preference  to  those  of  Puikilitic  (Gr., 
poikilos,  variegated)  and  Safiferous  (salt-yielding),  which  are 
in  use  by  some  geologists. 

206.  The  composition  of  the  New  Red  Sandstone  may 
be  said  to  be  arenaceous,  argillaceous,  calcareous,  mag- 
nesian, and  saline.     The  arenaceous  members  are  chiefly 
reddish  sandstones  of  various  fineness,  from  a  hard  quartz- 
ose  grit  to  a  brecciated  conglomerate.     Few  of  them  are 
laminated  or  micaceous,  and  the  thicker  beds  often  present 
curious  spherical  concretions  of  a  harder  texture,  containing 
some  foreign  substance  as  a  nucleus.     The  grains  of  the 
sandstones  are  of  a  clear  quartz,  merely  coloured  externally 
by  a  coating  of  the  red  oxide  of  iron,  as  if  the  debris  of  the 
rocks  from  which  they  were  derived  had  been  deposited  in 
ferruginous  waters.     The  argillaceous  members  are  usually 

578.  What  new  system  is  next  considered  1 

579.  What  does  this  system  overlie  ? 

580.  What  of  the  organic  remains  found  here  ? 

681.  What  of  the  composition  of  the  new  red  sandstone  T 
582.  What  of  the  arenaceous  ? 


NEW  RED  SANDSTONE  SYSTEM.  159 

called  "  marls,"  from  the  fact  of  their  often  containing  a 
little  calcareous  matter,  and  being  less  laminated  in  struc- 
ture than  the  coal  shales.  They  are  generally  red  ;  but  are 
sometimes  mottled  purple,  yellow,  and  green  (called  varie- 
gated marls),  and  contain  irregular  beds  and  plates  of  gyp- 
sum (sulphate  of  lime).  The  calcareous  members  vary 
from  an  almost  pure  carbonate  t)f  lime  to  an  admixture  of 
eirbonate  of  lime  and  carbonate  of  magnesia — ihence  called 
Alagnesian  Limestone.  They  vary  in  colour  from  an  ash- 
gray  to  a  cream-yellow;  are  sometimes  finely  laminated; 
at  other  times  granular  and  crystalline,  and  in  this  state 
called  dolomite,  after  M.  Dolomieu.  Frequently,  a  layer 
exhibits  a  cellular  or  vesicular  texture,  the  walls  of  the  cells 
being  sparry,  and  the  cells  themselves  filled  with  loose 
powdery  limestone.  This  cellular  structure  is  abundant  in 
the  magnesian  limestone  of  Durham,  and  has  received 
various  terms  from  the  shape  of  the  cells;  as  honeycombed; 
botryoidal,  composed  of  little  spherical  concretions  like  a 
bunch  of  grapes;  and  mammil/ary,  when  the  concretions 
assume  an  elongated  or  pap-like  shape.  These  concre- 
tionary and  cellular  forms  are  said  to  be  coralloidal — that 
is,  like  to  corals  in  shape;  but  they  have  nothing  to  do 
with  organic  structure,  being  merely  the  result  of  chemical 
or  mechanical  aggregation.  The  talinr  members  are  chiefly 
rock-salt,  which  occurs  in  white  crystallized  masses,  or 
reddened  by  the  argillaceous  sediment  among  which  it 
occurs.  Salt  springs  abound  in  the  new  red  sandstone, 
partly  from  the  shales  being  all  more  or  less  impregnated 
with  salt,  atid  partly  from  the  decomposition  of  the  rock-salt 
itself  Gypsum  occurs  among  the  marls  either  in  films  or 
foliated  fragments,  the  latter  variety  being  the  sclenite  of 
mineralogists ,  and  oxide  of  copper  is  the  green  colouring 
matter  of  the  shales. 


583.  Which  are  called  marls  ? 

584.  Which  are  magnesian  limestone  T 

585.  What  are  the  names  given  to  the  varieties  of  cellular  structure  f 

586.  How  are  they  formed  ? 

587.  What  of  rock  salt,  and  saline  springs  ? 

588.  Which  variety  of  marls  is  the  gypsum  and  the  selenite  ? 


H)J  GEOLOGY. 

207.  The  order  of  succession  among  tJif  nimbcrs  of  the 
new  red  sandstone  is  not  very  regular  or  persistent.  In 
England,  the  lower  part  of  the  series  consists  chieflv  o,1'  red 
sandstones  and  grits,  the  middle  of  magnesiau  limestones 
and  gypseous  marls,  and  the  upper  portion  of  variegated 
sandstones  and  marls,  enclosing  local  deposits  of  gypsum 
arid  rock-salt.  On  account  of  this  triple  succession,  Pro- 
fessor Sedgvvick  has  divided  the  system  into  the  following 
groups: — 

Description. 

"1.  VARIEGATED  MARLS — red,  with  bluish,  greenish,  and 
whitish  laminated  clays,  or  marls  holding  gypsum  gen- 
erally, and  rock-salt  partially  (as  in  Cheshire).  In- 
cluded in  these  marls  are  certain  beds  of  gray  and 
whitish  sandstones. 

6.  VARIEGATED  SANDSTONES— red  sandstones  with  white 
and  mottled  portions,  the  lower  parts  in  some  districta 
pebbly. 
"5.  LAMINATED  LIMESTONES  of  Knottingley,  Doncaster, 

&c.  with  layers  of  coloured  marls. 
4.  GYPSEOUS  MARLS — red,  bluish,  and  mottled. 
3.  MAGNESIAN  LIMESTONE — yellow  and  white;  of  various 
texture  and  structure ;  some  parts  full  of  fragmentary 


Groups. 


UPPER. 


MIDDLE. 


2.  MARL  SLATES — laminated  ;  impure  calcareous  rocks 
of  a  soft  argillaceous  or  sandy  nature. 

1.  RED  SANDSTONE — with  red  and  purple  marls,  and  a  few 
micaceous  beds.  The  grits  are  sometimes  white,  or 
yellow ;  and  pebbly.  When  conformable,  this  sand- 
stone occasionally  passes  into  the  coal  measures  on 
which  it  rests. 

It  must  not  be  supposed,  however,  that  the  system  always 
forms  so  complete  a  section-;  for  in  some  places  the  gypse- 
ous marls  predominate,  in  others  the  magnesian  limestone, 
while  in  several  a  mass  of  redstones,  with  subordinate  layers 
of  coloured  shales,  represent  the  whole  system.  The  fol- 
lowing table  shows  how  the  deposit  occurs  in  Germany, 
England  and  France;  from  which  the  student  may  also  learn 
the  important  fact,  that  it  is  by  general  types,  and  not  by 


LOWER. 


589.  What  of  the  order  of  succession  in  England  ? 

590.  Describe  the  tabular  arrangement  of  groups. 

591.  What  variations  from  this  1 

692.  What  is  shown  by  the  three  tables  ? 


NFW   RED  SANDSTONE  SYSTEM. 


161 


any  conventional   series  of  strata,  that  systems  are  to  be 
identified  in  different  countries: — 


GERMANY. 

Keuper       Marls       and 
Grits. 
Muschelkalk. 
Hunter  Sandstein. 
Stinkstein  ;  Rauwacke. 
Gypseous  Marls. 
Zechstein. 
Kupfer  Schiefer. 
Rothe-todte-liegende. 

ENGLAND. 

Variegated  Marls   and 
Grits. 

FRANCE. 

Marnes  Irisees. 

Muschelkalk. 
Gres  Bigarre. 

Variegated  Sandstone. 
Upper  Limestone. 
Gypseous  Marls. 
Magnesian  Limestone. 
Marl  Slate. 
Lower  Red  Sandstone. 

Gres  Rouge. 

208.  "  The  organic  remains  of  this  system,"  says  Pro- 
fessor Phillips,  "  though  few  in  number,  are  exceedingly 
interesting  to  Che  naturalist  and  geologist,  from  the  strong 
testimony  they  offer  of  the  successive  changes  of  the  living 
creation,  according  to  the  new  circumstances  of  the  land 
and  sea.     The  fossil  plants,  shells,  fishes,  and  reptiles  of 
this  system  appear  to  partake  both  of  the  character  of  those 
in  the  older  carboniferous,  and  the  newer  oolite  deposits. 
Calamites,  like  those  of  the  coal  formation,  are  mingled 
with  cycadeae,  resembling  closely  those  of  the  oolites.    Pro- 
ducts, so  common   in  mountain  limestone,  occur  in  the 
zechstein  with  terebratulse,  like  those  of  the  lias  and  oolites. 
Fishes  of  the  genus  palaBoniscus  here  occur  for  the  last 
time,  in  ascending  the  series  of  strata ;  and  here,  perhaps, 
for  the  first  time  we  have  remains  of  oviparous  quadrupeds 
— the  protosaurus  and  phytosaurus."    Exhibiting  this  tran- 
sition from  one  system  of  life  to  that  of  another,  the  new 
red  sandstone  has  been  regarded  as  the  boundary  between 
the  LOWER  and  UPPER  SECONDARY  STRATA — the  old  red 
sandstone,  mountain  limestone,  coal  measures,  and  new  red 
sandstone,  belong  to  the  lower  or  older  secondary  forma- 
tion ;  and  the  lias, oolite, and  chalk,  to  iheupper  or  younger 
secondary. 

209.  The  number  of  fossil  species  hitherto  detected  in  the 
new  red  sandstone  of  England  amounts  to  fifty  or  thereby, 
while  fully  thrice  that  number  has  been  found  in  France 

593.  What  of  the  organic  remains  ? 

594.  What  variety  of  fossils  is  found  here  1 

595.  Describe  the  two  series  of  secondary  strata  1 

596.  What  number  of  fossil  species  are  found  ? 


162  GEOLOGY. 

and  Germany.  These  consist  of  traces  of  marine  plants,  a 
few  terrestrial  plants,  several  zoophytes,  one  species  of  cri- 
noidea,  about  two  dozen  species  of  bivalves,  one  chambered 
shell,  several  fishes,  the  mutilated  skeletons  of  two  sauroid 
animals,  and  the  traces  of  footsteps,  called  ichnites,  from 
the  Greek  ichnon,  a  footmark.  Like  the  vegetation  of  the 
coal  era,  the  plants  of  the  new  red  sandstone  are  chiefly 
vascular  cryptogamia;  the  corals,  bivalves,  and  fishes,  are 
apparently  the  same  ;  and  it  is  only  in  the  chambered  shells, 
and  in  the  sauroids,  that  new  types  are  presented.  Alto- 
gether, the  system  seems  to  have  been  deposited  under 
circumstances  peculiarly  unfavourable  to  animal  and  vege- 
table life;  at  least  few  organic  exuviae  are  to  be  met  with 
in  its  strata. 

210.  The  igneous  rocks  associated  with  the  system  are 
chiefly  dykes  of  greenstone,  which  pass  indiscriminately 
through  the  magnesian  limestone,  coal  measures,  and  old 
red  sandstone.    These  dykes  belong  to  no  definite  volcanic 
era,  but  seem  to  have  been  formed  by  minor  forces  acting 
over  limited  extents.     The  granitic  rocks  of  the  primary 
period,  as  well  as  the  traps  of  the  old  red  sandstone  and 
carboniferous  measures,  establish  themselves  in  well-marked 
and  characteristic  ranges;   while  the  igneous  rocks  of  the 
new  red  sandstone,  lias,  and  oolite,  are  mere  local  effusions 
limited  to  dykes  and  partial  upheaves.     In  their  mineral 
character,  these  rocks  differ  little  from  the  traps  of  the  coal 
measures — consisting  chiefly  of  greenstone,  pitchstone,  and 
clay-stone  porphyry. 

211.  The  extent  of  country  over  which  this  system  is 
spread  is  not  well  ascertained.     Slight  traces  of  it  occur  on 
the  western  coast  and  islands  of  Scotland,  and  on  the  Fife 
shores  of  the  Forth;  it  occupies  a  wider  area  in  the  basin 
of  the  Solway  and  its  tributaries;  spreads  largely  over  the 
central  districts  of  England  from  the  Tyne  southwards ; 
and  is  found  in  the  north  of  Ireland.     Extensive  areas  are 
covered  by  it  in  the  continent  of  Europe — in  France,  Ger- 


597.  What  are  the  footmarks  called  ? 

598.  Of  what  do  the  igneous  rocks  here  consist? 

599.  What  of  the  extent  of  country  where  this  system  occurs? 


NEW   RED  SANDSTONE  SYSTEM.  163 

many,  Poland,  along  the  flanks  of  the  Alps,  in  Austria,  and 
between  the  Volga  and  the  Ural  mountains;  and,  accord- 
ing to  Professor  Hitchcock,  it  is  spread  over  considerable 
spaces  in  some  of  the  river  valleys  of  the  United  Slates. 

212.  The  physical  aspect  of  new  red  sandstone  districts, 
as  may  be  conjectured  from  the  limited  force  of  the  igneous 
rocks,  is  rather  flat  and  gentle.     There  are  no  picturesque 
crags,  mountain  ranges,  or  deep  ravines  to  diversify  the 
scenery;   which  consists  of  rounded  terraces  of  magnesian 
limestone,  and  level  expanses  of  red  sandstone  and  shales, 
here  and  there  dotted  with  a  gentle  eminence  of  limestone 
or  gravel.    Over  the  limestone  the  sward  is  thick  and  ver- 
dant, and  the  soil  above  the  red  sandstone  is  of  average  fer- 
tility; but  where  the  retentive  shales   spread  out   in  flat 
hollows,  they  ibrm  the  basis  of  extensive  morasses — as,  for 
example,  those  of  south  Lancashire,  in  England. 

213.  The  minerals  of  commerce  derived  from  the  forma- 
tion are  not  numerous — the  most  important  being  magnesia 
and  rock-salt.     The  magnesian  limestone,  when  reduced 
to  quick-lime,  is  employed  with  effect  on  certain  soils;  it 
furnishes  the  builder  with  mortar;  and  yields,  under  chemi- 
cal treatment,  the  magnesia  of  the  apothecary.     In  some 
localities  it  furnishes  a  beautiful  and  durable  building-stone; 
that  of  Bolsover  moor,  in  Derbyshire,  being  the  material 
employed  in  the  construction  of  the  new  houses  of  Parlia- 
ment.    Some  of  the  limestone  schists  are  also  suitable  for 
lithographic  purposes,  the  admired  German  blocks  being 
chiefly  derived  from  this  source.    Gypsum  is  obtained  from 
the  marls  of  the  series,  which  also  yield  the  main  supply  of 
rock-salt  in  various  parts  of  the  world- — such  as  Cheshire 
and  Worcester  in  England,  in  Spain,  Poland,  Germany,  and 
Austria.    This  salt  occurs  in  beds  or  irregular  masses,  from 
JO,  20,  or  30  feet,  to  120  feet  in  thickness;  is  of  various 
degrees    of  purity  and    colour.      Sometimes    it   contains 
scarcely  two  parts  in  the  hundred  of  foreign    matter,  at 
others  it  is  of  a  red  colour,  and  mixed  to  the  extent  of  half 


600.  What  of  its  physical  geography.? 

601.  Of  what  uses  are  the  magnesian  limestone  ? 

602.  What  of  t:  e  rock-salt  1 


1(54  GF.OLORY. 

its  bulk  with  earthy  impurities.  Urine,  or  salt-springs, 
which  often  issue  1'rom  this  deposit,  contain  from  20  to  30 
per  cent,  of  salt,  and  are  doubtlessly  derived  from  the  solu- 
tion of  the  solid  masses  by  subterranean  waters.  The 
kupfer-schieftr  of  Germany  is  worked  to  some  extent  as 
an  ore  of  copper;  but  no  other  metal  is  derived  from  the 
system. 

214.  The  formation  of  rock-salt  is  a  subject,  in  connexion 
with  this  system,  which  has  much  engaged  the  attention  of 
speculative  geologists.  The  sandstone  and  marls  with 
which  it  is  associated  are  evidently  derived  from  deposition 
in  water;  but  the  irregularity  of  the  salt  beds,  the  fact  of 
their  occurring  in  masses  of  vast  thickness,  and  the  soluble 
nature  of  the  compound,  all  point  to  a  somewhat  different 
origin.  At  present,  salt  lakes  and  superficial  accumula- 
tions of  salt  occur  in  various  parts  of  the  world,  and  these 
have  furnished  data  for  reasoning  as  to  the  saliferous  depo- 
sits of  earlier  eras.  Salt  lakes  are  chiefly  derived  from  salt 
springs,  and  being  subjected  to  the  vaporizing  influence  of 
the  sun,  which  carries  off  only  fresh  vapour,  their  waters 
become  in  time  saturated  writh  saline  matter.  But  water 
can  hold  only  a  fixed  amount  of  salt  in  solution  ;  and  so 
soon  as  this  amount  is  attained,  the  salt  begins  to  fall  to  the 
bottom  by  its  own  gravity.  In  the  course  of  ages,  these 
layers  will  form  a  thick  bed.  interstratified,  it  may  be,  with 
mud,  or  other  earthy  sediment;  and  if  the  lake  should  be 
ultimately  dried  up,  the  salt  will  constitute  a  deposit  some- 
thing analogous  to  the  rock-salt  of  the  new  red  sandstone. 
Such  is  the  process  which  some  geologists  have  advanced 
to  account  for  the  formation  of  rock-salt — supposing  mat 
portions  of  the  seas  of  deposit  were  occasionally  cut  off 
from  connexion  with  the  main  ocean,  and  subjected  to  a 
rapid  evaporating  power,  without  receiving  fresh  accessions 
of  vvater.  The  limited  extent  of  rock-salt  basins  seems  to 
favour  such  a  theory;  but  when  we  consider  the  frequency 
of  disturbance  by  volcanic  forces  in  earlier  ages,  and  the 
fact  of  many  of  these  deposits  occurring  near  to,  or  in  cen- 


603.  Whence  are  brine  springs  derived  ? 

604.  How  is  the  formation  of  rock-salt  accounted  for  f 


NEW  RED  SANDSTONE  SYSTEM.  165 

nexion  with,  mountain  elevations,  it  is  more  than  probable 
that  igneous  action,  as  well  as  a  high  atmospheric  tempera- 
ture, had  to  do  with  their  formation.  If  such  were  the 
origin  of  rock-salt,  it  must  have  been  formed  during  the 
deposition  of  other  systems  than  the  new  red  sandstone; 
and  this  geological  research  has  confirmed ;  lor  although 
the  most  extensive  accumulations  do  occur  amid  the  sand- 
stones and  shales  of  the  system  under  review,  still,  deposits 
of  considerable  thickness  are  found  in  connexion  with 
oolite,  green-sand,  and  tertiary  rocks,  while  numerous  salt 
springs  issue  from  the  carboniferous  strata. 

215.  The  formation  of  magnesian  limestone  has  also 
given  rise  to  several  theories.  Minute  quantities  of  mag- 
nesia occur  variously  combined  in  the  crust  of  the  earth ;  but 
only  in  the  limestones  of  this  system  is  it  sufficiently  de- 
veloped to  constitute  a  peculiar  and  distinguishing  feature. 
The  most  prevalent  hypotheses  advanced  to  account  for 
this  peculiarity  are — first,  that  the  carbonate  of  magnesia 
was  deposited  at  the  same  time  as  the  carbonate  of  lime; 
and,  second,  that  it  was  subsequently  injected  in  the  form 
of  gaseous  vapour.  Neither  hypothesis  seems  to  account 
for  all  the  phenomena  presented ;  although  the  former  is 
that  which  admits  of  most  extensive  application. 

EXPLANATORY    NOTE. 

NEW  RED  SANDSTONE  SYSTEM.-1 — In  some  recent  works,  it  has  been 
attempted  to  arrange  the  rocks  of  this  system,  as  developed  in  Eng- 
land, under  two  grand  divisions;  the  first  including  the  lower  new  red 
sandstone  and  magnesian  limestone,  and  the  second  the  variegated 
sandstones  and  gypseous  marls.  This  arrangement  has  been  made  in 
order  to  facilitate  comparison  with  the  contemporaneous  systems  of 
continental  and  eastern  Europe.  In  Germany  and  the  neighbouring 
countries  the  former  division  corresponds  with  the  Rothe-todte-lifgende, 
and  the  latter  with  what  is  now  generally  known  as  the  Triassic 
system  (so  called  from  its  being  readily  divisible  into  three  groups — 
the  Bunter  Sandstein,Muschelkalk,  and  Keuper  Marls).  To  the  rocks 
of  eastern  Europe,  which  seem  contemporaneous  with  the  new  red 
sandstone,  Mr.  Murchison  has  applied  the  term  Permian  system,  from 

605.  What  renders  it  probable  that  igneous  as  well  as  aqueous  agency 

his  bnen  employed  T 

606.  What  is  the  probable  theory  of  the  formation  of  magnesian 

limestone  T 

6^7.  Explain  the  terms  of  th*  note. 
8 


166  GEOLOGY. 

their  being  widely  developed  in  the  ancient  kingdom  of  Permia,  which 
extends  for  several  hundred  miles  along  the  western  flanks  of  the  Ura- 
lian  chain,  and  thence  westward  to  the  river  Volga. 

ZECHSTEIN  (mine-stone) — so  called  from  its  containing  a  deposit 
(Kupfer-schiefer,  or  copper-slate)  which  is  worked  as  an  ore  of  copper, 
and  the  underlying  sandstone  has  received  the  name  Rothe-todte-liegende 
(red  dead-lier),  because  it  is  of  a  red  colour,  is  dead  or  worthless  as  far 
as  any  metallic  ore  is  concerned,  and  underlies  the  real  metallic  de- 
posit. The  other  terms,  Stinkstein,  Muschelkalk,  Ores  Rouge,  &c.  re- 
quire no  translation. 

ICHNITES,  or  fossil  footsteps,  present  a  curious  example  of  the  means 
by  which  geologists  are  enabled  to  decipher  the  history  of  the  earth. 
Most  people  must  have  observed  how  distinct  the  impressions  of  the 
feet  of  birds  and  other  animals  are  often  left  on  the  mud  or  sand  of 
ebbing  rivers.  If  this  mud  should  remain  exposed  to  the  sun  and  air 
till  sufficiently  dried,  and  then  be  overlaid  by  some  new  sediment,  the 
impression  of  the  foot  will  lbrm  a  mould  into  which  the  new  matter 
will  be  deposited.  Should  the  two  layers  ever  be  consolidated  into 
stone,  on  being  separated,  the  one  would  present  a  mould,  and  the 
other  a  cast  of  the  footsteps  ;  and  this  is  precisely  what  takes  place 
among  the  strata  of  the  earth's  crust.  FossJ  footsteps  have  been  dis- 
covered in  the  new  red  sandstone  of  Cocklemuir  in  Dumfriesshire,  and 
in  that  of  Hildburghausen  in  Saxony,  supposed  to  be  those  of  reptiles  5 
hence  termed  sauroidichnites.  Others  have  been  detected  in  the  sand- 
stones of  Connecticut,  United  States,  and  ascribed  to  gigantic  birds 
allied  to  the  Ostrich  family ;  consequently  called  Ornithictmites,  from 
the  Greek  words  ornis,  a  bird,  and  ichnon,  a  trace  or  footprint.  To 
these  Professor  Hitchcock  adds  a  third  class,  tetrapodichnites,  or  the 
footsteps  of  some  unknown  four-footed  animal. 


OOLITIC    SYSTEM. 
LIAS,  OOLITE,  AND  WEALDEN  GROUPS. 

216.  After  the  deposition  of  .the  new  red  sandstone,  a  fur- 
ther change  was  effected  upon  the  general  conditions  of  the 
globe,  so  as  to  produce  not  only  an  entirely  different  set  of 
strata,  but  alsi  different  races  of  plants  and  animals.  In 
most  districts,  the  red  sandstones  and  magriesian  limestone 
were  upheaved,  to  form  new  land,  while  poriions  of  the 
former  dry  land  were  submerged  beneath  the  ocean.  By 
this  process  of  elevation  and  depression  the  courses  of  pre- 
vious rivers  would  be  altered,  former  seas  circumscribed 
and  rendered  more  shallow,  plants  and  animals  subjected 

608.  How  are  fossil  footsteps  explained,  and  where  found  ? 

609.  What  system  is  here  considered,  and  what  groups  compose  it  '• 

610.  What  geological  reasoning  is  presented  7 


OOLI  nc  >YSTKM.  167 

to  a  new  distribution,  and  thus  a  different  set  of  deposits 
would  necessarily  ensue.  Instead  oi  mngnesian  rocks,  we 
have  dark  argillaceous  and  oolitic  limestones;  for  varie- 
gated saliferous  marls,  we  have  bine  pyritous  clays;  and 
instead  of  red  and  mottled  sandstones,  yellow  calcareous 
grits.  All  this  points  to  a  new  epoch  in  the  terrestrial  con- 
ditions of  the  world  ;  and  to  the  system  of  strata  thus  depo- 
sited geologists  apply  the  term  oolitic  (Gr.,wn,  an  egg,  and 
lif/ios,  a  stone),  from  the  rese'rnblance  which  the  texture  of 
many  of  the  beds  bear  to  the  roe  or  eggs  of  a  fish.  Oolite, 
or  roesfone,  is  an  aggregate  of  rounded  calcareous  particles, 
varying  from  the  size  of  a  millet-seed  to  that  of  a  marble — 
the  smaller  being  almost  perfectly  spherical,  the  larger  irre- 
gular, and  having  their  interstices  filled  with  calcareous 
matter  or  broken  shells.  The  system  in  England  com- 
prises three  well-defined  groups;  namely,  the  Lias,  the 
Oolite  proper,  and  the  Wealden  clays. 

217.  T/ie  Lias,  the  lowest  group  in  the  system,  is  com- 
posed of  dark  argillaceous  limestones,  bluish  clays,  and 
shales.  The  clays  in  general  predominate,  and  occur  with 
interstratified  limestones;  they  contain  occasional  layers  of 
jet  or  other  coal:  ironstone  in  septsria  is  not  unfrequent; 
and  many  of  the  shales  abound  in  bitumen  and  iron  pyrites. 
As  indicated  by  the  name  (lias,  c  rruption  of  layers"),  the 
limestones  are  finely  stratified,  and  i we  evidently  been  de- 
posited in  tranquil  waters.  Most  of  th  shales,  in  addition 
to  their  bituminous  and  pyritous  qualities,  are  impregnated 
with  muriate  of  soda  (common  salt),  and  with  the  sulphates 
of  magnesia  and  soda:  and  Mr.  Bakewell  states  that  it  is 
not  uncommon,  after  wet  weather,  for  the  Yorkshire  sea- 
cliffs,  which  are  composed  of  these  shales,  to  ignite  spon- 
taneously, and  burn  for  several  months.  The  Oolite  is 
more  varied  in  its  composition,  consisting  of  oolite  lime- 
stones, calcareous  grits,  or  conglomerates,  yellowish  sands, 
and  clays  all  more  or  less  calcareous.  The  peculiar  rounded 
grains  which  constitute  the  oolitic  texture,  consist  either 

611.  Define  oolite. 

612.  What  of  the  lowest  group? 

613.  What  of  their  various  composition,  and  of  the  shale*  1 

614.  What  of  the  oolite  composition  ? 


168  OEOLOT/Y. 

entirely  of  lirne,  or  of  an  external  coating  of  lime,  collected 
round  minute  particles  of  sand,  coral,  shells,  &,c. ;  the  grits 
are  composed  of  sand,  lime,  fragments  of  shells  and  corals; 
arid  many  of  the  clays  present  the  same  brecciated  texture. 
The  Wealden  group  (from  \\\e  wealds  or  wolds  of  Kent  and 
Sussex,  where  the  deposit  prevails)  consists  of  beds  of 
bluish  clay,  argillaceous  limestones,  impure  oolites,  and 
ferruginous  sandstones.  Nodular  ironstone  occurs  in  the 
clays,  and  beds  of  pisiform  (Lat.,  pisum,  a  pea)  iron-sand 
are  occasionally  met  with,  while  oxide  of  iron  is  more  or 
less  diffused  through  the  whole  group.  Fossil  plants  are 
abundant ;  and,  as  may  be  expected  from  this  circumstance, 
local  traces  of  coal  are  not  unfrequent. 

218.  Taking  the  whole  systtm  into  account,  it  is  apparent 
that  calcareous  and  argillaceous  compounds  prevail;  indeed 
it  may  be  said  to  be  an  argillo-calcareous  deposit,  including 
subordinate  layers  of  sandstone,  bands  of  ironstone,  and 
traces  of  coal.     Among  the  lias  strata,  dark  hues  prevail; 
among  the  oolite,  cream-yellow  and  ochraceous  colours; 
the  clays  of  the  wealden  are  dark  blue,  while  its  other  beds 
partake  of  a  ferruginous  tint. 

219.  With  regard  to  the  succession  among  the  strata,  no 
very  regular  order  is  observed ;  though  no  fact  in  gf  ology  is 
better  established  than  the  supra  position  of  the  lias,  oolite, 
and  wealden,  as  above-described.     The  lias  is  the  most 
extensive  and  persistent  of  the  three  groups,  and  seems  to 
have  been  deposited  over  wider  areas ;  the  oolite  is  less 
persistent,  being  often  interrupted  by  changes  from  sand- 
stones to  brecciated  grits,  and  from  grits  to  oolitic  lime- 
stones; and  the  wealden  is  the  least  extensive,  being  justly 
regarded  as  a  half  estuary  half  marine  deposit,  peculiar  to 
certain  districts.     Taking  the  system  as  developed  in  Eng- 
land, the  following  is   the  ascertained   order  among  the 
strata,  between  which  and  the  contemporaneous  rocks  of 
the  continent  there  is  no  essential  mineral  or  fossil  dis- 
tinction : —  « 


615.  How  is  the  wealden  group  distinguished? 

616.  What  variety  is  in  the  whole  system  T 

617.  What  of  the  order  of  succession  ? 


OOLITIC  SYSTEM. 


WEALDEX 


OOLITE. 


LIAS 


i 


TJlue  laminated  clays,  containing  concretional  iron- 
stone and  thin  layers  of  argillaceous  limestone. 
(The  weald  clay.) 

Sands  and  sandstones,  frequently  ferruginous  ;  beds 
of  clay  and  sandy  shale,  all  more  or  less  calcare- 
ous. (Hastings  sands.) 

Various  estuary  limestones,  alternating  with  sands 
and  clays.  (Purbeck  beds.) 

Portland  oolite ;  calcareous  irony  sand  and  concre- 
tions; and  a  calcareous  clay,  locally  called  "  Kim- 
meridge  clay." 

Coralline  oolite  (coral  rag);  calcareous  sands  and 
grits;  Oxford  clay,  including,  layers  of  impure 
clayey  limestone. 

Oolitic  and  shelly  strata  (Cornbrash) ;  forest  mar- 
ble ;  Bath  oolite ;  yellow  sandstones,  divided 
by  clays  and  calcareous  sands  ;  marls  and  fuller's 
earth. 

TThick  beds  of  dark-coloured  bituminous  shale;  beds 
of  pyritous  clay  ;  and  indurated  lias  marls. 

Lias  limestones  and  clays ;  bands  of  ironstone ; 
layers  of  jet  and  lignite  ;  sandstones  more  or  less 
calcareous. 

229.  The  organic  rrmains  of  the  oolitic  system  are  very 
numerous,  and  have  long  attracted  the  attention  of  geolo- 
gists. They  show  a  decided  advance  upon  pre-existing 
races,  inasmuch  as  insects,  amphibious  reptiles,  and  mam- 
malia, majte  their  appearance  in  the.  animal  kingdom  ; 
while  new  tribes  of  vegetables,  such  as  the  cycadere,  lilaceas, 
&c.  are  added  to  the  Ibrmer  Flora.  The  organisms  of  the 
lias,  the  oolite,  and  the  lower  members  of  the  wealden, 
indicate  the  marine  origin  of  these  deposits;  those  of  the 
upper  weald  an  estuary  character,  from  the  comminglement 
of  fresh  water  with  marine  species.  With  this  distinction, 
the  Fauna  and  Flora  of  this  epoch  may  be  thus  summarily 
detailed: — Plants — seaweeds;  a  few  equisetums;  many 
ferns  allied  to  the  sphenopteris,  pecopteris,  &c.  of  the  coal 
measures;  cycadeae,  allied  to  the  existing  cycas  revoluta 
and  pine-apple;  coni  ferae,  resembling  the  yew  and  pine; 
besides  lilacese  and  other  undescribed  genera.  Animals — 
^oophytes,  more  like  existing  species  than  those  of  the 

618.  Explain  the  order  of  the  wealden  group. 

619.  How  is  it  with  the  two  other  groups  ? 

620.  What  of  the  organic  remains  of  this  system? 

621.  Describe  the  fauna  and  flora  of  this  epoch. 


170  GEOLOGY. 

mountain  limestone  and  silurian  rocks;  crinoidea,  chiefly 
the  apiocrinite  and  pentacrinite ;  star-fishes,  resembling  the 
common  ophiura  and  asterias ;  echinida  (sea-urchins),  of 
which  the  cidaris  is  one  of  the  most  beautiful  and  abun- 
dant; shell-fish,  both  vivalves,  univalves,  and  chambered; 
annulosa,  like  the  common  serpula  and  land-worm  ;  crus- 
tacea,  resembling  the  lobster-tribe ;  insects  like  the  beetle 
and  dragon-fly;  fishes  belonging  chiefly  to  the  ganoidia; 
reptiles  allied  to  the  tortoise,  to  the  crocodile,  and  gavial  of 
existing  rivers,  but  differing  widely  in  their  external  forms 
and  modes  of  existence;  mammalia,  two  or  three  speci- 
mens of  small  marsupial  animals  allied  to  the  opossums. 
In  the  upper  or  fresh-water  wealden,  there  are  no  zoophytes 
or  marine  rnollusca ;  but  there  are,  according  to  Phillips, 
various  land  plants,  fresh-water  bivalves  and  univalves, 
some  fishes,  sauroid  animals,  and  remains  of  turtles,  both 
fresh-water  and  marine. 

221.  The  fossils  most  characteristic  of  the  system  are  the 
cycadeaB,  of  which  the  stems,  fruit,  and  leaves  are  found  in 
abundance,  the  sea-urchins,  the  ammonites  of  various  ge- 
nera and  gigantic  size,  the  sauroid  reptiles,  the  ptero-dac- 
tyles  or  flying-lizards,  the  fresh-water  and  marine  turtles, 
and  the  marsupial  mammalia.  The  cycadese  occur  princi- 
pally in  the  upper  or  fresh-water  portion  of  the  weald, 
intermingled  with  the  stumps  and  prostrate  trunks  of  trees. 
They  are  found  most  plentifully  in  what  is  locally  desig- 
nated the  "  dirt-bed"  of  Portland — a  stratum  of  dark  argil- 
laceous mud,  which  must  at  one  time  have  been  the  soil  in 
which  they  and  other  vegetables  flourished,  but  which,  by 
a  submergence  of  the  land,  was  converted  into  the  bottom 
of  an  estuary,  over  which  other  strata  of  clay,  limestone,  and 
s;md  were  deposited.  "  At  the  distance  of  two  feet,"  says 
Bakewell,  "  we  find  an  entire  change  from  marine  strata  to 
strata  once  supporting  terrestrial  plants;  and  should  any 
doubt  arise  respecting  the  original  place  and  position  of 
these  plants,  there  is,  over  the  lower  dirt-bed,  a  stratum  of 
fresh-water  limestone,  and  upon  this  a  thicker  ditt-bed, 


622.  What  fossils  are  characteristic  ? 

623.  What  geological  argument  is  thence  derived  T 


OOLITIC  SYSTEM. 


171 


containing  not  only  the  cycadeae,  but  stumps  of  trees  from 
three  to  seven  feet  in  height,  in  an  erect  position,  with 
their  roots  extending  beneath  them.  Stems  of  trees  are 
found  prostrate  upon  the  same  stratum;  some  of  them  are 
from  twenty  to  twenty-five  feet  in  length,  and  fiom  one  to 
two  feet  in  diameter.  The  following  section  of  a  cliff  in 
Dorset  exhibits  very  clearly  proofs  of  the  alternation  from 


i 


a  a  a,  Portland  Stone  (marine  formation) ;  6,  Dirt-bed,  consisting  of 
black  mould  and  pebbles  (temporary  dry  land) ;  c,  Burrstone,  and  d, 
Calcareous  Slate  (both  of  fresh- water  formation). 

marine  strata  to  dry  land  covered  with  a  forest,  and  of  a 
subsequent  submergence  of  the  dry  land  under  a  river  or 
lake  which  deposited  fresh-water  limestone." 

222.*O/"fAe  radiata,  mollusca,  and  crustacea  of  this  era, 
it  may  be  observed,  that  while  they  differ  essentially  from 
those  of  the  older  secondary  strata,  they  approximate  in 
form  to  existing  races.  The  gigantic  and  prolific  crinoidea 
of  the  mountain  limestone  had  disappeared,  and  been  suc- 
ceeded by  a  few  dwarfish  specimens  of  apiocrinite  and  penta- 
crinite ;  while  the  cidaris  (see  fig.  p.  172),  clypeus,  and  other 
echinida  (sea-urchins),  attest  a  higher  degree  of  orgnniza- 

*  (See  Appendix.)    . 

524    Describe  the  diagram. 

525.  What  difference  is.  observed  from  those  of  the  older  secondary 
strata  ? 


173 


GKOLOaV. 


lion  among  radiated  animals.  Among  the  shell-fish,  the 
grypli(Bat  trigonia,  ottrca,  and  ammonite,  are  the  most  cha- 
2  ^  3 


1.  Cidaris  intermedia;  2.  Gryphaea  incurva ;  3.  Trigonia  costata ; 
4.  Ostrea  deltoidea. 

racteristic — hundreds  of  species  of  the  latter  having  left 
their  remains  in  the  most  perfect  state  of  preservation  in 
the  shales  and  limestones  of  the  lias.  The  ammonite  (of 
which  two  species,  and  a  section  of  the  interior,  is  figured 
below)  receives  its  name  from  its  resemblance  to  the  curved 
horn  on  the  head  of  the  statue  of  Jupiter  Ammon.  It  was 


1.  Ammonites  obtusus  ;  2.  Section  of  Ammonites  obtusus,  showing  the 
interior  chambers  and  siphuncle  ;  3.  Ammonites  nodosus. 

a  chambered  shell  belonging  to  the  cephalopodous  division 
of  mollusca — that  is,  having  its  organs  of  motion  arranged 
round  the  head;  and  had  many  congeners  in  the  euompha- 
lus,  nautilus,  orthoceratite,  hamite  (hook-shaped),  scaphite 
(boat-shaped),  baculite  (staff-shaped),  and  other  many-cham- 
bered shells.  It  is  one  of  the  most  widely-distributed  mol- 
luscs in  the  secondary  strata,  and  is  found  of  all  sizes,  from 
that  of  a  pin's  head  to  three  or  four  feet  in  diameter.  The 
economy  of  the  ammonite  destined  it  in  general  to  live  at 

626.  Describe  the  first  diagrams. 

627.  What  of  the  other  diagrams  ?    - 

628.  Describe  the  wonderful  structure  of  the  ammonite. 


OOLITIC  SYSTEM.  173 

the  bottom  of  deep  waters,  but  to  be  able  to  rise  at  pleasure 
to  the  surface.  For  this  purpose  the  outer  chamber  (o  o) 
of  the  wreathed  shell  was  fitted  for  the  reception  oi  the 
animal,  while  the  interior  chambers  (i  i)  were  hollow,  so  as 
to  make  the  whole  structure  nearly  of  the  same  weight  as 
the  element  in  which  it  moved.  Through  all  of  these 
chambers  an  elastic  tube  passed  by  means  of  a  pipe  or 
siphuncle  (s  s),  the  tube  being  in  connexion  with  the  cavity 
of  the  heart,  which,  under  ordinary  circumstances,  was 
filled  with  a  dense  fluid.  When  alarmed,  or  wishing  to 
descend,  the  animal  withdrew  itself  within  the  outer  cham- 
ber, and  the  pressure  upon  the  cavity  of  the  heart  forced 
the  fluid  into  the  siphuncle,  so  as  to  increase  the  gravity  of 
the  shell,  by  which  means  it  readily  sunk  to  the  bottom. 
On  the  other  hand,  when  wishing  to  ascend,  it  had  only  to 
project  its  arms,  and  the  fluid,  being  freed  from  the  pressure, 
returned  from  the  siphuncle  to  the  cavity  of  the  heart,  thus 
restoring  the  whole  structure  to  its  ordinary  floating  gravity 
As  the  pressure  of  water  at  the  bottom  ot  the  sea  would 
break  the  plates  of  any  ordinary  shell,  as  it  does  a  bottle 
when  it  is  lowered  to  a  great  depth,  the  shell  of  the  am- 
monite has  been  strengthened  by  a  curious  kind  of  internal 
arch-v.ork,  so  as  to  be  able  to  resist  the  weight  of  the  in- 
cumbent fluid.  This  arch-work  so  completely  meets  all 
human  ideas  of  ingenious  contrivance  for  the  purpose  which 
it  was  destined  to  serve,  as  to  form  one  of  the  most  striking 
examples  of  that  adaptation  of  means  to  ends  which  prevails 
throughout  the  works  of  nature,  and  which  is  so  well  fitted 
to  impress  the  conviction  of  a  great  designing  First  Cause. 
223.  T7te  insects,  Jt*ke*t  and  rrptiles  of  the  oolitic  system 
have  greatly  attracted  the  attention  of  naturalists  and  geolo- 
gists; and,  as  might  be  expected  from  remains  so  obscure, 
have  given  rise  to  much  diversity  of  opinion.  The  insects 
discovered  in  the  slaty  limestones  of  the  true  oolite  at  St>- 
lenliafen  in  Germany,  and  Stonesfield  in  England,  some- 
\vhat  resemble  the  dragon-fly  and  serricorn  beeiles  of  the 
present  day.  The  fishes  present  the  enameled  scale  and 

629.  What  reflections  are  suggested  1 

630.  What  or' the  inserts,  fishes  and  reptiles  of  this  system  1 


174  GF.OLOfJY. 

unequally-lobed  tail  of  the  cartilaginous  order,  and  find  a 
distant  analogue  in  the  existing  rc.ttracioii  of  the  Austral- 
asian seas.  It  WHS  slated,  that  the  hones  and  teeth  of  rep- 
tiles had  been  found  in  the  marls  of  the  new  red  sandstone; 
but  in  the  lias  and  the  strata  above  it,  the  exuviae  of  these 
animals  are  so  abundant,  and  of  such  vast  size,  that  the 
epoch  in  which  these  strata  were  deposited  has  not  unaptly 
been  termed  "  the  age  of  reptiles."  Of  these  there  are  ter- 
restrial and  marine  chelonida  (tortoises  and  turtles);  lizards, 
whose  arms  and  legs  were  fitted  with  a  filmy  membrane, 
like  bats,  to  enable  them  to  fly  (pterodactyles) ;  amphibious 
saurians,  like  the  gavial  and  crocodile;  and  water  saurians, 
to  which  there  is  now  no  existing  analogy.  Of  these  sau- 
roid  or  lizard-shaped  reptiles,  the  ichthyosaurus  and  plesio- 
saurus  are  most  abundantly  disseminated  through  the  upper 
secondary  formations.  The  general  form  of  the  ichthyo- 
saurus (Gr.,  ichthy?,  a  fish,  and  saurus,  a  lizard)  appears 
from  its  skeleton  (see  fig.)  to  have  been  not  unlike  that  of 
a  crocodile,  with  the  substitution  of  paddles  for  feet.  The 
head  is  lengthened  into  a  narrow  pointed  muzzle,  and  the 


Skeleton  of  Ichthyosaurus  communis. 

jaws  armed  with  sharp  and  formidable  teeth.  The  skele- 
ton of  the  I.  tenuirostris  (slender-muzzle)  usually  measures 
about  four  feet  in  length ;  but  detachrd  remains  of  other 
species  have  been  found,  indicating  a  length  of  twenty  or 
even  thirty  feet.  The  plesiosaurus  (so  called  from  its 
greater  affinity  to  the  lizard  tribe  than  to  fishes)  was  dis- 
tinguished by  the  extraordinary  length  of  its  neck,  which, 
in  the  commonest  species  (P.  doKchofleirus,  or  long-necked), 

63.1.   Whnt  of  their  variety? 
631;.  Describe  the  diagram. 


OOLITIC  SYSTEM.  175 

occupies  nearly  half  the  entire  length  of  the  animal.  The 
head  is  very  small  in  proportion,  and  the  tail  is  short,  stout, 
and  pointed.  The  vertebras  of  the  neck  exceed  in  number 
those  of  any  other  animal  known.  It  is  conjectured  by 
Mr.  Conybeare,  by  whom  the  first  scientific  investigation  of 
this  saurian  was  made,  that,  as  it  breathed  air,  and  had  fre- 
quent need  of  respiration,  it  generally  swam  upon  or  near 
the  surface  of  the  water,  arching  back  its  long  neck  like 
the  swan,  and  plunging  it  downwards  at  the  fishes  that 
passed  within  its  reach.  Its  length  seems  to  have  been 
from  ten  to  fifteen  feet.  From  the  nature  of  their  extremi- 
ties, both  the  ichthyosaurus  and  plesiosaurus  must  have 
moved  with  great  difficulty  upon  land,  and  seem  princi- 
pally to  have  inhabited  the  waters.  Besides  these,  geolo- 
gists enumerate  many  other  species  of  saurians — aquatic, 
amphibious,  and  terrestrial ;  such  as  the  megalosaurus  (great 
saurian),  geosaurus  (land  saurian),  hylae.osaurus  (forest  sau- 
rian), tdeosaurus  (perfect  saurian),  &c. 

2*24.  Respecting  the  mammalia  of  this  era,  no  very  satis- 
factory data  have  yet  been  procured,  the  only  evidence 
being  two  or  three  lower  jaw-bones  from  the  slaty  limestone 
of  Stonesfield.  Though  some  French  geologists  have  at- 
tempted to  ascribe  a  sauroid  character  to  these  remains,  it 
is  the  opinion  of  Cuvier,  Dr.  Buckland,  and  Professor  Owen, 
that  they  belong  to  true  didelphys  (dis,  two,  delphys,  wombs) 
animals;  that  is,  double-wombed,  or  marsupial  creatures, 
like  opossum  and  kangaroo.  Should  this  be  the  case — 
and  comparative  anatomy  is  too  unerring  in  its  deductions 
to  admit  of  any  doubt — then  in  the  upper  oolite  are  we  for 
the  first  time  made  acquainted  with  mammalia  in  the  his- 
tory of  creation.  "  The  close  approximation  of  these  fossil 
animals,"  says  Profess  >r  Owen,  "  to  marsuphl  genera,  now 
confined  to  New  South  Wales  and  Van  Dieman's  Land, 
leads  us  to  reflect  upon  the  interesting  correspondence  be- 
tween other  organic  remains  of  the  British  oolite,  and  other 
existing  forms  now  confined  to  the  Australian  continent 

633.  What  conjecture  has  been  indulged  as  to  the  plesiosaurus  T 

634.  What  other  species  are  found  ? 

635.  What  proof  of  the  mammalia  of  this  era  T 

636.  To  what  genus  of  animals  are  they  supposed  to  belong  f 


I7<5  GEOLOGY. 

and  adjoining  seas.  Here,  for  example,  swims  the  cestra- 
cion,  which  has  given  the  key  to  the  nature  of  the  palates 
from  our  oolite,  now  recognized  as  the  tenth  of  congeneric 
gigantic  forms  of  cartilaginous  fishes.  Not  only  trigonia, 
but  living  terebratulcB  exist,  and  the  latter  abundantly  in 
the  Australian  seas,  yielding  food  to  the  cestracion,  as  their 
extinct  analogues  doubtless  did  to  the  allied  cartilaginous 
fishes  called  acrodi  and  psammodi,  &c.  Auracariae  and 
cycadeous  plants  likewise  flourish  on  the  Australian  conti- 
nent, where  marsupial  quadrupeds  abound,  and  thus  appear 
to  complete  a  picture  of  an  ancient  condition  of  the  earth's 
surface,  which  has  been  superseded  in  our  hemisphere  by 
other  strata,  and  a  higher  type  of  mammalian  organization." 
Professor  Phillips  remarks  to  the  same  effect — "  It  is  inte- 
resting to  know  that  the  earliest  mammalia  of  which  we 
have  yet  any  trace  were  of  the  marsupial  division,  now 
almost  characteristic  of  Australia,  the  country  where  yet 
remain  the  trigonia,  cerithium,  isocardia,  zamia,  tree-fern, 
and  other  forms  of  life  so  analogous  to  those  of  the  oolitic 
periods." 

225.  "During-  the  oolitic  period"  continues  the  latter 
authority,  "  the  arctic  land  was  covered  by  plants  like  those 
of  hot  regions,  whose  vegetable  remains  have  locally  gene- 
rated coal-beds,  adorned  by  coleopterus,  neuropterus,  and 
other  insects,  among  which  the  flying  lizafd  (pterodactyl us) 
spread  his  filmy  wings.  The  rivers  and  shores  were  watched 
by  saurians  more  or  less  amphibious  (rnegalosaurus,  iguano- 
don),  or  tenanted  by  reptiles  which  by  imaginative  men 
have  been  thought  to  be  the  originals  of  our  gavials  and 
crocodiles,  while  the  sea  was  full  of  forms  of  zoophyta, 
mollusca,  articulosa,  and  fishes.  Undoubtedly  the  general 
impression,  gathered  from  a  survey  of  all  those  monuments 
of  earlier  creations,  is,  that  they  lived  in  a  warm  climate; 
and  we  might  wonder  that  the  result  of  all  inquiry  has 
shown  no  trace  of  man  or  his  works,  did  we  not  clearly 
perceive  the  oolitic  fossils  to  be  all  very  distinct  from  exist- 
ing types,  and  combined  in  such  different  proportions,  as 


637.  What  of  Australia  ? 

638.  What  geological  reasoning  is  hazarded  ? 


OOUTIC  5.VSIT.M.  177 

to  prove  that  circumstances  then  prevailed  on  the  globe 
materially  different  from  what  we  now  see,  and  probably 
incompatible  with  the  existence  of  those  plants  and  animals 
which  belong  to  the  creation  whereof  man  is  the  appointed 
head." 

22(3.  The  igneous  rocks  associated  with  the  system  in 
England  belong  chiefly  to  the  trappean  order.  In  no  case 
have  they  caused  much  displacement  or  great  disturbance 
among  the  strata,  being  gentle  outbursts  of  trap-tuff,  or  in- 
tersecting dykes  of  greenstone.  These  dykes  are  always 
connected  with  some  volcanic  axis  of  the  carboniferous 
period,  and  seem  to  have  been  among  the  last  upheaving 
efforts  of  the  trappean  era.  In  Caithness,  granitic  rocks 
pass  through  the  oolitic  strata,  but  with  this  exception — 
the  igneous  rocks,  which  have  upheaved  or  altered  the  sys- 
tem, belong  either  to  the  latest  trap,  or  the  earliest  volcanic 
epochs. 

227.  The  extent  of  country  occupied  by  the  oolite  is  by 
no  means  extensive,  though  partial  deposits  are  very  gene- 
rally disseminated   over   the    globe.     It   is  most  fully  de- 
veloped in  England,  occupying  the  eastern  sea-board  from 
Yorkshire  to  Dorset ;  it  occurs  in  a  small  patch  at  Brora  in 
Sutherland,  in  Syke,  and  other  of  the  Hebrides,  and  par- 
tially in  Ireland  and  Wales.   Portions  of  the  system  are  also 
found    in  France   and  Germany;    skirting   the    Alps;    in 
Spain  and  the  Balearic  islands;  flanking  the  Apennines 
and  Atlas  range;  on  the  southern  slope  of  the  Himmalehs; 
but  no  true  equivalents  to  the  European  oolite  have  hitherto 
been  detected  in  America. 

228.  Unless  in  England,  the  oolitic  system  is  not  so  ex- 
tensively developed  as  to  impart  any  distinctive  geographi- 
cal ftature;  and  there,  though  pleasing,  the  aspect  is  tame 
compared  with  that  imparted  by  the  older  strata.    The  lime- 
stones in  general  form  rounded  escarpments  over  the  sub- 
jacent clays,   "  so   that    several    longitudinal   hollows  and 
ridges  undulate  the  area  occupied  by  the  system."     None 


639.  What  of  the  igneous  rocks  found  here  7 

640.  In  what  localities  does  this  system  occur  I 
U  11     What  of  its  physical  geography  f 


178  GKOLORY. 

of  these  ridges  are  of  great  height  (400  to  600  feet),  but 
they  are  dry  and  fertile;  and  thus  present  an  agreeable  con- 
trast with  the  level  river  valleys  occupied  by  the  lias  and 
wealden  clays. 

229.  In  an  economical  point  of  view,  the  rocks  of  this 
system  are  by  no  means  unimportant.  The  lias  limestones 
generally  consist  of  from  80  to  90  per  cent,  of  carbonate 
of  lime,  combined  with  bitumen,  alumine,  and  iron ;  and 
when  the  latter  mineral  enters  largely  into  their  composition, 
they  form,  when  burned,  a  lime  which  has  the  properly  of 
setting  under  water.  The  finer  kinds  of  lias  receive  a 
polish,  and  are  used  for  lithographic  purposes.  The  lias 
clays  are  often  much  impregnated  with  bitumen  and  iron 
pyrites,  and  will  burn  slowly  when  laid  in  heaps  with  fagots 
and  kindled.  By  this  process  the  sulphur  of  the  pyrites  is 
decomposed,  and  combining  with  the  oxygen  of  the  atmo- 
sphere, and  with  a  portion  of  the  alumina  in  the  shale, 
forms  sulphate  of  alumina,  or  «the  alum  of  commerce. 
During  the  sulphur  monopoly,  several  patents  were  ob- 
tained for  the  extraction  of  sulphur  from  iron  pyrites 
(sulphuret  of  iron)  most  of  which  would  have  been  profit- 
ably adopted,  had  the  native  produce  of  Sicily  continued 
at  the  then  exorbitant  rate.  Iron  has  also  been  extracted 
from  the  ironstone  and  pisiform  iron-sands  of  the  wealden 
group;  and  jet  (which  is  simply  altered  coniferous  wood) 
occurs  in  the  same  measures.  Fuller's  earth,  at  one  time 
so  valuable  in  the  useful  arts,  is  found  in  the  upper  oolite  in 
beds  of  great  thickness.  It  is  essentially  composed  of 
silica,  alumina,  and  24  per  cent,  of  water,  and,  like  other 
soft  aluminous  marls,  possesses  in  a  high  degree  the  power 
of  absorbing  grease;  hence  its  value  in  cleansing  and 
scouring  woollen  stuffs.  Some  of  the  oolite  sandstones 
form  excellent  building  material,  such  as  those  of  Bathtind 
Portland;  several  ornamental  marbles  are  obtained  from 
the  same  group ;  while  the  Purbeck  beds  of  the  wealden 
furnish  the  most  prevalent  paving-stones  in  London. 


642.  What  of  the  economical  uses  of  these  groups? 
64  1.  Name  some  of  the  minerals  and  earths  yielded. 


.    OOLITIC  SYSTKM.  179 

EXPLANATORY    NOTE. 

LIAS. — The  term  Liassic  is  commonly  applied  to  this  group  by  recent 
authors. 

COR.VBRASH  is  said  to  derive  its  name  from  the  facility  with  which  it 
disintegrates  and  yields  to  the  plough,  being,  according  to  the  provin- 
cial term,  brashy  or  breaky  ^enough  to  enable  the  plough  to  prepare  the 
surface,  where  it  prevails,  for  the  growth  of  grain  or  corn. 

SAUROID  ANIMALS  are  generally  classed,  according  to  their  organs 
of  locomotion  ;  namely,  swimmers,  or  those  fitted  with  paddles,  as  the 
ichthyosaurus,  plesiosaurus,  mososaurus,  phytosaurus,  steneosaurus, 
teleosaurus,  saurodon,  &c. ;  with  limbs  like  mammalia,  and  fitted  for  a 
terrestrial  life,  the  megalosaurus  and  iguanodon  ;  analogous  to  living 
amphibia,  the  protosaurus,  geosaurus,  pleurosaurus,  hylaeos  lurus,  &c. 

THE  CHAMBERED  SHELLS  of  this  system  include  many  genera,  all  of 
which  are  fitted  with  interior  hollow  chambers  and  siphunrles.  The 
most  common  are  the  ammonite,  nautilus,  euomphalns,  bellerophon, 
goniatite,  hamite  (hamus,  a  hook),  scaphite  (sr.apha,  a  boat),  orthocera- 
tite  (orthos,  straight,  keras,  a  horn),  bacuhte  (bactUum,  a  staff),  lituite, 
(lituus.  an  augur's  rod  or  crosier),  &c.  &c.  Sometimes  the  shelly  mat- 
ter of  the  ammonite  has  been  entirely  destroyed,  leaving  only  a  cast  of 
the  interior,  each  chamber  in  this  case  playing  upon  auother  by  the 
intricate  jointings  of  the  septa,  or  divisional  lines ;  such  casts  are 
known  by  the  name  of  ammonites  catena,  or  ammonite  chains. 

CRETACEOUS,  OR  CHALK  SYSTEM. 

230.  Immediately  overlying  the.  wealden,  and  forming 
the  upper  portion  of  the  secondary  formation,  occurs  a  set 
of  calcareous,  argillaceous,  and  arenaceous  strata,  dis- 
tinguished in  Europe  as  the  Cretaceous  System,  from  its 
containing  the  well-known  mineral,  chalk  (Lat.,  crtta).  In 
this  system,  as  stated  in  par.  140,  the  arenaceous  members 
are  no  longer  staridstones,  but  loose  unsolidified  sands;  the 
argillaceous  beds  are  generally  sort  and  marly  clays;  and 
the  calcareous,  instead  of  compact  or  crys'alline  limestones, 
present  that  soft  earthy  texture  which  prevails  in  chalk. 
All  this  attests  a  comparative  recentness  of  formation,  apart 
from  great  pressure,  long-continued  chemical  action,  or  the 
indurating  effects  of  heat.  The  strata  occupy  very  limited 
spac  's,  and  being  decidedly  of  marine  origin,  point  more 
to  detached  and  inland  seas  as  the  areas  of  their  deposit, 

644.  Define  the  terms  of  the  note. 

645.  What  variety  of  chambered  shells  ? 

646.  Define  the  cretaceous  system  and  its  strata. 

647.  What  inferences  are  drawn  by  geologists  from  the  nature  of 

chalk  ? 


180  ftEOLOc;v. 

than  to  the  shores  or  bays  of  the  ocean.  Being  thus,  as  it 
were,  a  local  deposit,  and  of  a  thickness  not  exceeding  803 
or  900  feet,  the  chalk  has  been  more  thoroughly  explore  d 
than  any  of  the  older  systems,  and  its  fossils  more  rigidly 
compared  with  existing  species.  Upon  investigation  it  has 
been  fjurid  that  it  embraces  three  well-marked  groups; 
namely,  the  Grem-sand,  the  Gault,  and  Chalk. 

23 1 .  The  composition  of  these  groups  is  a  1  most  sufficient- 
ly indicated  by  their  respective  terms.  The  Green-sand, 
which  forms  the  lower  division,  is  so  named  from  its  green 
colour,  which  it  owes  to  a  chloritous  silicate  of  iron. 
These  sands,  however,  are  not  uniformly  green,  but  partake 
of  ochraceous  and  yellow  tints;  they  present  various  de- 
grees of  fineness;  and  not  unfrequently  contain  cherty 
bauds,  irregular  deposits  of  Fuller's  clay,  and  ochre.  In 
England,  they  are  usually  divided  into  the  Lower  and 
Upper  green-sands,  because  of  a  bed  of  soft  bluish  marly 
clay  which  occurs  about  the  middle  of  the  group.  Re- 
garding this  bed  as  subordinate,  the  green-sand  is  easily- 
distinguished  from  the  rest  of  the  system  by  its  arenaceous 
composition  and  greenish  hues.  The  Gault,  or  golt  (a 
local  term),  overlies  the  green-sand,  and  is  not  of  great 
thickness,  nor  very  regular  in  its  occurrence.  It  is  a  bluish 
chalky  clay,  which  effervesces  strongly  on  the  application  of 
acids;  it  is  interstratified  with  layers  of  green-sand,  and 
holds  irregular  balls  of  argillaceous  ironstone  and  iron 
pyrites.  In  some  districts  the  gault  assumes  a  reddish  tint, 
from  the  iron  it  contains ;  but  in  other  respects  its  compo- 
sition is  very  persistent.  The  Chalk,  which  forms  the 
upper  group  of  this  system,  is  too  well  known  to  require 
description.  It  consists  chiefly  of  carbonate  of  lime,  has 
an  earthy  texture,  and  is  so  soft  as  to  yield  to  the  nail. 
Though  generally  white,  it  sometimes  passes  into  a  dusky 
gray,  or  even  red  colour,  as  in  the  north  of  England  ;  and 
where  it  has  come  in  contact  with  igneous  rocks,  it  is  in- 

648.  What  groups  are  marked  ? 

649.  To  what  does  green-sand  owe  its  colour  t 

650.  What  is  gault  and  its  varieties  1 

651.  Of  what  does  chalk  consist? 

652.  How  is  it  found  in  England  T 


CRETACEOUS,  OR  rHAl.K  SYSTEM.  .         181 

durated,  and  of  a  crystalline  texture,  like  that  of  statuary 
marble.  In  England,  the  chalk  strata  average  from  600  to 
803  feet  in  thickness,  and  are  usually  divided  into  the  lower 
and  upper  beds ;  the  former  being  more  compact,  of  a 
dusky  white  varied  with  green  grains,  and  containing  few 
flints — the  latter  being  a  soft  white  calcareous  mass,  with 
chert  nodules  and  regular  layers  of  flints.  Traces  of 
stratification  are  scarcely  distinguishable  in  the  mass  of  the 
chalk,  but  are  clearly  evinced  by  the  lines  of  flints  and 
other  nodular  concretions.  In  some  of  the  continental 
chalks,  carbonate  of  magnesia  prevails  to  the  extent  of  8 
or  It)  per  cent.,  giving  to  such  beds  a  still  more  earthy 
texture. 

232  The  order  of  succession  among  the  strata  is  such 
as  has  been  shown  above ;  but,  to  render  it  more  distinct, 
we  may  transcribe  the  following  sectional  detail  of  the 
system  as  it  occurs  in  the  south  of  England  : — 

("UPPER   CHALK — usually   a    white   soft   calcareous 

Jmass,  with  chert  nodules  at  regular  intervals,  and 
layers  of  flints. 
LOWER   CHALK — harder   and    less   white  than  the 
!       upper  ;  sometimes  varied  by  green  grains  ;  gene- 

i     rally    with   fewer   flints.     (Red  in  the  north  of 
England.) 
GAULT,  OR  CHALK  MARL — beds  of  bluish  laminated 
clays,  h  ghly  calcareous,  with  layers  of  green- 
sand,  and  ferruginous  nodules. 

("UPPER  GREEN-SAND — a  mass  of  sands,  occasionally 
indurated  to  chalky  or  cherty  sandstone,  of  green 

!or  grayish-white  colour,  with  nodules  of  chert. 
Soft  bluish  clay,  with  green  grains. 

GREEN-SAND.  ^  LOWER  GREEN-SAND — a  considerable  mass  of  green, 

or  ferruginous  sands,  with  layers  of  chert;  local 

beds  of  blue   clay  ;  rocks  of  chalky  or   cherty 

limestone ;  and  deposits  of   ochre    and  fuller's 

(_     earth. 

All  the  members  detailed  above  do  not  occur  in  other  cre- 
taceous districts;  for  example,  there  is  no  green-sand  in  the 
north  of  England;  no  chalk  along  the  Carpathians;  no 
gaultin  America;  while  in  South  America  the  system  is 
represented  by  impure  chalky  beds  of  no  great  thickness. 

653.  Explain'the  tabular  arrangement. 

654.  How  is  it  in  different  districts  ? 


182 


GEOLOGY. 


233.  The  organic  remains  found  in  the  system  are  emi- 
nently marine.  There  are  very  few  plants,  and  these 
chiefly  of  marine  types,  such  as  algae,  confervae,  and  other 
sea-weeds.  Rare  fragments  of  ferns,  cones  of  coniferous 
trees,  cycadites,  and  dicotyledonous  wood,  have  been  de- 
tected in  the  green-sand  ;  and  a  patch  of  lignite  is  said  to 
occur  in  the  lower  chalk,  near  Rochelle  in  France.  Re- 
specting this  deposit,  M.  Brogniart  thinks  it  may  have  been 
formed  by  the  local  submergence  of  a  peat  rnoss;  but  gene- 
rally speaking,  there  is  no  formation  so  destitute  of  terres- 
trial organisms  as  the  chalk.  Among  the  animal  remains, 
sponges,  corals,  star-fishes,  annulosa,  univalve,  bivalve,  and 
chambered  mollusca,  Crustacea,  fishes  and  reptiles,  are 
found  in  abundance;  but,  with  one  exception,  mammalia 
are  not  known  in  the  cretaceous  rocks.  The  same  races 
which  appeared  in  the  oolite  appear  also  in  the  chalk,  but 
of  very  different  genera;  so  much  so,  that  it  has  been  ob- 
served thtit  the  cretaceous  system  contains  genera  never 
found  in  any  rocks  more  ancient  or  more  modern.  "There 


1.  Pecton  quinque-costatus  ;  2.  Flagiostoma  spmosum  ;  3.  Hamitea 
intermedius  ;  4.  Spatangus  cor-anguinum  ;  5.  Galerites  albogalerus  ; 
6.  Scaphites  striatus  ;  7.  Belemnites  mucronatus. 

appears  no  sufficient  evidence,"  says  Professor  Phillips,  "  in 
the  fossils  of  this  system  to  justify  any  positive  inference  as 
to  the  character  of  the  climate  then  prevailing  in  the  north- 


655.  What  of  its  organic  remains  ? 

656.  Describe  the  figures  of  the  animal 


fossils  in  the  diagrams. 


CRETACEOUS,  OR  CHALK  SYSTEM.  183 

ern  zones :  but  we  may  be  sure  that  the  sea  was  very  little 
disturbed  by  inundations  from  the  land,  otherwise  ferns  and 
other  plants,  and  not  fuci,  would  have  been  found  in  the 
sandy  strata."  It  is  true  that  the  evidence  respecting  the 
climate,  and  other  conditions  of  the  cretaceous  era,  is  still 
imperfect;  but  the  recently  discovered  remains  of  the 
highest  order  of  mammalia  (quadrumana,  or  monkey  tribe) 
point  to  a  tropical  climate;  and  this  fact,  taken  in  conjunc- 
tion with  the  occurrence  of  cycadites,  seems  to  establish 
a  temperature  little  different  from  that  which  prevailed 
during  the  wealden  epoch.  The  foregoing  engraving  re- 
presents a  few  of  the  more  characteristic  fossils  belonging 
to  the  system. 

234.  Igneous  rocks  are  no  where  associated  with  the 
chalk  in  England;  but  basalt  and  other  traps  break  through 
and  overlie  the  strata  in  the  north  of  Ireland — the  Giant's 
Causeway  presenting  one  of  the  finest  examples  of  this 
connexion.  In  the  Pyrenees,  cretaceous  strata  are  said  to 
be  in  contact  with  granitic  rocks;  but  generally  speaking, 
the  system  has  escaped  with  fewer  displacements  by  igfne- 
ous  agency  than  any  of  the  earlier  formations.  As  has  been 
stated,  where  chalk  comes  in  contact  with  igneous  dis- 
charges, the  heat  has  rendered  it  hard  and  crystalline  like 
primary  marble.  The  same  effects  have  been  produced  by 
enclosing  pounded  chalk  in  an  iron  tube,  and  subjecting  it 
to  the  heat  of  a  furnace. 

23.5.  The  geographical  extent  of  the  system  is  limited, 
when  compared  with  earlier  formations.  It  is  pretty  ex- 
tensively developed  in  the  south  arid  south-east  of  England, 
filling  up  the  hollows  and  basins  left  by  the  oolite  and  lias. 
It  appears  in  the  north  of  Ireland  overlaid  by  basalt  and 
other  trap  rocks;  but  is  unknown  in  Wales  or  in  Scotland. 
It  is  spread  over  wide  areas  in  France  and  Germany;  and 
is  found  about  Dresden,  in  the  Alps,  Carpathians,  and  Py- 
renees. According  to  Professor  Rogers,  it  occupies  a  vast 

657.  Which  of  the  mammalia  have  been  found  here  ? 

658.  Where  are  igneous  rocks  found  in  connection  with  this  system, 

and  how  explained  ? 

659.  What  of  the  extent  of  the  system,  and  the  physical  aspect  of 

the  cretaceous  districts  T 


184  GEOLOGY. 

area  in  the  North  American  states;  and,  by  recent  ac- 
counts, has  been  detected  in  the  western  river-plains  of 
South  America. 

236.  The  physical  aspect  of  chalk  districts   is  easily 
distinguished  by  the  smooth  flowing  outline  of  the  hills  and 
valleys.     Here  there  are  no  rugged  arid  lofty  peaks,  as  in 
the  earlier  formations;  no  tabular-looking  escarpments,  as 
in  the  lias  and  oolite;  but  easy   undulations,   forming  in 
their  extent  the  well-known  "  wolds"  or  "  downs"  of  south- 
ern England.    These  downs  are  characterized  "  as  covered 
with  a  sweet  short  herbage,  forming  excellent  sheep  pasture, 
generally    bare   of  trees,  and   singularly   dry  even  in  the 
valleys,  which  for    miles   wind  and    receive    complicated 
branches,    all    descending  in  a  regular  slope,  yet  are  fre- 
quently left  entirely  dry;  and,  what  is  more  singular,  con- 
tain no  channel,  and  but  little  other  circumstantial  proof 
of  the  action  of  water,  by  which  they  were  certainly  exca- 
vated."    Chalk  districts  thus    possess    great  amenity  and 
rural    beauty,  and  are  as  yet  but  little  broken   up  by  the 
enterprise  of  modern  agriculture. 

237.  The  minerals  of  commerce   derived  rrom   the  sys- 
tem are  by  no  means  numerous.     Chalk  is  used  for  many 
purposes  in  the  arts  and  in  agriculture:  it  furnishes  polishing 
paste,  and  the  well-known  whitening  of  the  painter.     Beds 
of  fuller's  earlh  occur  in  the  lower  green-sand,  and  in  some 
districts  the  more  indurated  strata  of  the  group  produce  a 
rou2h  building-stone.     Flint  is  one  of  the  most  valuable 
products  of  the  system  ;  furnishing  material   or  the  manu- 
facture of  china  and  porcelain,  flint  glass,  and  gun-flints — 
the  latter  having  been  in  universal  use  before  the  invention 
of  the  percussion  cap. 

238.  TliR  formation  of  flint,  within  a  mass  so  different 
in  composition  as  chalk,  is  still  in  some  respects   an  un- 
solved problem  in  geology.     It  occurs  in  nodular  masses 
of  very  irregular  forms  and  variable  magnitude;  some  of 
these  not  exceeding  an  inch,  others  more  than  a  yard  in 
circumference.     Although  thickly  distributed  in  horizontal 


660.  What  of  its  economical  uses  ? 

661.  How  is  the  formation  of  flint  explained  T 


CRETACEOUa,    OR    CITALK    SYSTEM.  lo 

layers,  they  are  never  in  contact  with  each  other,  each 
nodule  being  completely  enveloped  by  the  chalk.  Exter- 
nally, they  are  composed  of  a  white  cherty  crust;  internally, 
they  are  of  gray  or  black  silex,  and  often  contain  cavities 
lined  with  calcedony  and  crystallized  quartz.  When  taken 
from  the  quarry  they  are  brittle  and  full  of  moisture,  but 
soon  dry,  and  assume  their  well-known  hard  and  refractory 
qualities.  Flints,  almost  without  exception,  enclose  re- 
mains of  sponges,  alcyonia^  echinida,  and  other  marine 
organisms,  the  structures  of  which  are  often  preserved  in 
the  most  delicate  and  beautiful  manner.  In  some  speci- 
mens the  organism  has  undergone  decomposition,  and  the 
space  it  occupied  either  left  hollow,  or  partially  filled  with 
some  sparry  incrustation.  From  these  facts,  it  would  seem 
that  flints  are  as  much  an  aggregation  of  silex  around  some 
organized  nucleus,  as  septaria  (par.  192)  are  aggregations 
of  clay  and  carbonate  of  iron.  This  is  now  the  generally 
received  opinion:  and  when  it  is  remembered  that  the  or- 
ganisms must  have  been  deposited  when  the  chalk  was  in 
a  pulpy  state,  there  can  be  little  difficulty  in  conceiving 
how  the  silex  dissolved  through  the  mass  would,  by  chemi- 
cal affinity,  attach  itself  to  the  decaying  organism.  Chalk 
is  composed  of  carbonate  of  lime,  with  traces  of  clay,  silex, 
and  oxide  of  iron ;  flint,  on  the  other  hand,  consists  of  98 
per  cent,  of  pure  silex,  with  a  trace  of  aiumine,  oxide  of 
iron,  and  lime.  Silex  is  quite  capable  of  solution:  it 
occurs  in  the  hot  springs  of  Iceland  and  most  thermal 
waters ;  has  been  found  in  a  pulpy  state  within  basalt ; 
forms  the  tabasheer  found  in  the  cavities  of  the  bamboo, 
and  the  thin  pellicle  or  outer  covering  of  canes,  reeds, 
grasses,  &c. ;  and  siliceous  concretions  are  common  in  the 
fruits  and  trees  of  the  tropics.  All  these  facts  point  to  a 
very  general  diffusion  of  silex  in  a  state  of  solution;  and 
whatever  may  have  caused  its  abundance  in  the  waters 
during  the  deposition  of  the  upper  chalk,  there  can  be  little 

662.  What  of  the  nuclei  of  flint  T 

663.  What  of  the  relative  composition  of  chalk  and  flint  ?  . 
.  664.  How  is  silex  known  to  be  capable  of  solution  I 

665.  Where  is  it  found  7 


186  GEOLOGY. 

doubt  respecting  the  mode  in  which  it  has  been  collected 
around  the  organic  remains  of  these  early  seas. 

EXPLANATORY  NOTE. 

THE  ORIGIN  OF  CHALK,  so  different  in  its  texture  and  appearance 
from  all  other  limestones,  has  given  rise  to  many  hypotheses.  tf  There 
appears  no  evidence,"  says  Mr.  Brande,  "  of  its  having  been  deposited 
from  chemical  solution  ;  but,  on  the  other  hand,  it  bears  marks  of  a 
mechanical  deposit,  as  if  from  water  loaded  with  it  in  fine  division. 
And  upon  this  principle,  some  gleam  of  light  may  perhaps  be  thrown 
upon  the  enigmatical  appearance  of  the  flints  ;  for  it  is  found,  that  if 
finely-powdered  silica  be  mixed  with  other  earthy  bodies,  and  the 
whole  diffused  through  water,  the  grains  of  silica  have,  under  certain 
circumstances,  a  tendency  to  aggregate  into  small  nodules  ;  and  in 
chalk,  some  grains  of  quartz  are  discoverable."  There  can  be  little 
doubt  that  such  has  been  the  original  state  of  chalk,  from  whatever 
source  derived  ;  for,  without  the  supposition  that  the  calcareous  par- 
ticles were  diffused  through  the  waters  in  which  it  was  deposited,  it 
were  impossible  to  account  for  almost  any  of  the  phenomena  connected 
with  it  as  a  formation.  But  while  such  has  evidently  been  the  origin 
of  the  great  mass  of  the  chalk  rocks,  it  does  not  preclude  the  chemi- 
cal agency  of  springs,  or  the  organic  efforts  of  secreting  animalcules. 
All  other  limestones  in  the  crust  of  the  earth  point  to  a  complex  for- 
mation, in  which  mechanical,  .chemical,  and  organic  agencies  have 
been  concerned  ;  and  it  is  but  reasonable  to  suppose  that  chalk  is  the 
result  of  similar  forces. 

BELEMNTTES  (Gr.,  belemnon,  a  dart) — a  genus  of  fossil-chambered 
shells,  perforated  by  a  siphuncle,  and  so  called  from  their  straight  dart- 
like  form.  Unlike  other  chambered  shells,  they  were  internal;  that 
is,  enclosed  within  the  animal  like  the  pen  of  the  squid  and  cuttle-fish. 
Many  of  these  belemnites  are  of  great  size,  showing  the  gigantic 
nature  of  the  cephalapods  to  which  they  belonged.  Being  long,  straight, 
and  conical,  they  are  commonly  known  by  the  vernacular  names  of 
«*  thunder  stones"  and  "  thunder  bolts." 

TERTIARY  STRATA. 

239.  THE  TF.RTIARY  SYSTEM  comprises  all  the  regular 
strata  of  limestone,  marl,  clay,  sand,  and  gravel  which 
occur  above  the  chalk.  Before  the  labours  of  the  celebrated 
Cuvier  and  M.  Brogniart,  these  beds  were  regarded  as  mere 
superficial  accumulations,  not  referable  to  any  definite 
period.  Now,  however,  they  are  recognized  as  constituting 


666.  What  of  the  origin  of  chalk  ? 

667.  What  geological  reasoning  is  here  authorized  1 

668.  What  are  belemnites,  and  their  vernacular  names  t 

669.  What  strata  does  the  tertiary  system  comprise  ? 

670.  How  is  it  distinguished  from   alluvial  or   superficial    accumu- 

lations 1 


TERTIARY  STRATA.  137 

a  distinct  formation — differing  from  the  cretaceous  not  only 
in  its  mineral  composition,  but  in  the  higher  order  of  or- 
ganisms which  it  contains,  and  from  the  superficial  sands 
and  clays,  in  being  regularly  stratified,  and  in  imbedding 
the  remains  of  animals  distinct  from  existing  races.  In 
general  the  strata  are  loosely  aggregated,  are  of  no  great 
thickness,  and  present  appearances  which  indicate  frequent 
alternations  of  marine  a.nd  fresh-water  agencies.  Thus, 
marine  remains  are  found  in  some  beds,  while  others  con- 
tain exclusively  land  animals  and  plants,  and  fresh-water 
shells.  The  whole  suit  being  less  consolidated  than  any 
of  the  secondary  systems,  and  containing  plants  and  ani- 
mals approaching  to  existing  forms,  it  presents  a  freshness 
of  aspect  which  serves  to  distinguish  it  from  older  deposits; 
at  the  same  time  the  regularity  of  its  deposition  prevents  it 
from  being  mistaken  for  any  mere  alluvial  accumulation. 
In  general  it  occupies  very  limited  and  detached  areas,  as 
if  it  had  been  formed  in  shallow  inland  seas  and  estuaries, 
to  which  the  waters  of  the  ocean  at  times  had  access,  and 
where  at  other  periods  fresh-water  inundations  prevailed. 
Another  essential  difference  between  the  tertiary  and  the 
more  ancient  formations  consists  in  the  fact,  that  the  latter 
maintain  a  wonderful  uniformity  in  their  composition  and 
character  all  over  the  globe;  whereas  the  former  present 
almost  as  many  distinctions  in  composition  as  there  are 
areas  of  deposit.  For  this  reason  it  is  impossible  to  give  a 
description  applicable  to  all  tertiary  strata ;  those  of  Eng- 
land and  France,  however,  may  be  taken  as  types  suffi- 
ciently characteristic. 

240.  Respecting  the  composition  of  the  system,  arenaceous 
and  argillaceous  beds  may  be  said  to  prevail,  with  inter- 
stratified  limestones,  calcareous  grits,  and  marls.  The  are- 
naceous members  are  either  pebbly  conglomerates  of  a  rusty 
yellow,  or  sands  little  indurated  and  variously  tinted  by  the 
oxide  and  silicate  of  iron.  The  sands  are  seldom  suffi- 
ciently consolidated  to  form  sandstones;  and  the  conglo- 


671.  What  of  its  composition  f 

672.  What  of  the  arenaceous  variety  1 

673.  What  variety  in  the  argillaceous  b«di  1 


I*5?  OfcoLOttY. 

merates  are  often  mere  layers  of  rolled  pebbles,  without 
any  cementing  matrix.  The  argillaceous  beds  also  present 
many  varieties;  some  being  almost  pure  laminated  clay  of 
a  dull  blue  colour,  others  of  a  brownish  tint,  with  a  slight 
admixture  of  sand,  while  many  pass  into  marls  more  or  less 
calcareous.  None  of  these  clays  are  so  compact  as  to  form 
shales;  indeed  lamination  is  more  frequently  absent  than 
otherwise,  there  being  nothing  except  their  fossils  and  asso- 
ciated beds  to  distinguish  them  from  the  clays  of  subsequent 
alluvial  valleys.  The  calcareous  layers  are  still  more  varied 
in  their  composition  and  aspect,  and  bear  no  resemblance 
to  the  indurated  half-crystalline  limestones  of  older  forma- 
tions. The  marine  limestone  of  the  Paris  basin  is  of  a 
coarse  sandy  texture;  that  of  Austria  a  rough  coralline 
rock  :  the  fresh-water  beds  near  Weimar  are  hard  and  corn- 
pact  ;  those  of  other  districts  are  soft,  marly,  and  full  of 
shells.  In  some  localities  marls  are  so  calcareous  as  to  be 
used  as  limestones,  while  in  others  they  pass  into  soft  fria- 
ble clays.  From  this  extreme  diversity  of  composition,  it 
is  evident  that  many  agencies  have  been  concerned  in  the 
deposition  of  the  tertiary  system,  and  that  most  of  them 
have  been  of  a  local  character,  producing  results  not  differ- 
ing widely  from  those  of  the  present  day. 

241.  The  succession  of  strata  is  no  less  varied  than  their 
mineral  composition.  As  at  the  present  day  distant  rivers 
are  depositing  different  sorts  of  material  at  one  and  the 
same  time,  so  in  distant  tertiary  basins  different  strata  vari- 
ously succeed  each  other.  Luckily,  none  of  the  deposits 
are  of  great  thickness,  and  as  they  have  been  closely  exam- 
ined for  the  sake  of  their  fossils,  the  alternations  of  the 
beds  have  been  pretty  accurately  ascertained.  The  follow- 
ing is  a  descending  section  of  the  Paris  basin,  according  to 
Cuvier  and  Brogniart: — 

6.  UPPER  FRESH-WATER  GROUP — marl s,  marly  sands,  shelly  limestone, 
and  siliceous  or  burr  limestone. 

4  UPPER  MARINE  GROUP — marls,  sands  and  sandstones  of  a  white  or 
ochraceous  colour,  and  loosely  aggregated  ;  thin  layers  of  lime- 
stone. 

674.  What  of  the  calcareous  layers? 

675.  Explain  the  table  7 


TERTTARY    STRATA. 


189 


3    LOWER  FRESH-WATER — marls,  gypsum  (sulphate  of  lime),  with  bonea 
of  animals,  and  siliceous  limestones. 


I.  LOWER  MARINE — consisting  principally  of  a  coarse  sandy  limestone 
(calcaire  grassier),  with  calcareous  marls 


sand. 


and  layers  of  greenish 


1.  PLASTIC  CLAY  GROUP — consisting  of  bluish  plastic  clays,  with  layers 

of  sand,  beds  of  lignite,  and  rolled  pebbles.     Supposed  to  be  of 
estuary  origin. 

Although  a  very  different  succession  takes  place  among  the 
teriiaries  of  the  south  of  England,  yet  there  is  sufficient 
resemWance  in  the  position  and.  aggregation  of  their  strata, 
as  well  as  in  their  organic  remains,  to  establish  the  fact, 
that  they  belong  to  the  same  epoch  as  the  rocks  of  the  Paris 
basin.  The  annexed  section  shows  the  order  of  their  oc- 
currence to  the  south  of  London : — 

4.  BAGSHOT  SANDS. 

3.  LONDON  CLAY — of  a  dull  gray,  or  blue,  or  ochraceous  colour;  often 

full  of  green  grains.    Septaria  and  other  ferruginous  nodules  occur 

in  some  parts.     Numerous  fossils. 

2.  PLASTIC  CLAY  AND  SANDS — sands  of  various  colours,  with  occasional 

beds  of  lignite  ;  also  layers  of  sandy  clay,  with  or  without  sheila. 
1.  SANDS — green  and  ferruginous,  accompanied  by  flint  pebbles,  oyster 
shells,  &c. 

In  other  parts  of  England  the  order  of  occurrence  is  some- 
what different.  It  may  be  stated,  however,  in  general 
terms,  that  the  sands  are  most  extensively  developed;  the 
clays  chiefly  in  the  southern  basins;  while  at  Oxford, 
Ramsholt,  &c.  the  upper  beds  consist  of  a  coarse  conglo- 
merate of  corals,  sand,  pebbles,  shells,  &c.  locally  known 
as  the  "Crag,"  and  s  >  calcareous  in  some  places  as  to  be 


I.  Hirer  Thames:   2.  Marine  sands:   3.  London  clay;  4.  Plastic  clay 
and  sands  ;  5.  Chalk  with  flints;  6.  Green-sand  and  Gault-clay. 


676.  What  of  the  tabular  arrangement  1 
677    Expla  n  the  diagram. 
9 


190  GEOLOGY. 

used  as  a  limestone.  As  with  the  Paris  and  English  depo- 
sits, so  with  other  tertiary  basins  in  Europe:  those  of 
southern  France,  Spain,  Italy,  Austria,  Hungary,  &c. — all 
showing  an  irregular  succession  of  clays,  sands,  marls,  lig- 
nites, and  gypsum,  which,  when  examined  in  relation  to 
their  positions,  modes  of  aggregation,  and  fossils,  are  clearly 
referable  to  the  same  period  of  formation.  Tne  foregoing 
engraving  illustrates  the  tertiary  deposits  of  the  Thames 
basin,  with  the  subjacent  chalk  and  green-sand. 

242.  -As  to  the  extent  of  country  occupied  by  tertmry  de- 
posits, there  is  yet  no  very  accurate  knowledge,  inasmuch 
as  many  sands  and  clays,  now  regarded  as  the  alluvium  of 
existing  valleys,  may  hereafter  be  referred  to  this  system ; 
and  several  areas  of  gravel,  now  looked  upon  as  tertiary,  be 
classed  with  more  recent  accumulations.  As  developed  in 
Europe,  the  system  spreads  over  wide  areas,  all  remarkable 
for  their  conformation  and  connexion  with  the  outline  of 
existing  seas.  Indeed,  were  the  islands  and  continent  of 
Europe  to  be  submerged  to  the  depth  of  600  or  600  feet, 
the  waters  of  the  German,  Baltic,  English  Channel,  and 
Mediterranean  seas,  would  cover  most  of  the  tertiary  strata, 
showing  that,  with  the  exception  of  the  general  elevation 
which  raised  them  into  dry  land,  there  has  been  compara- 
tively little  subterranean  disturbance  since  the  time  they 
were  deposited.  In  Britain  the  formation  is  exhibited  in 
Hampshire,  Isle  of  Wight,  in  the  basin  of  London,  and 
from  the  Thames  northwards  along  the  coast  to  the  mouth 
of  the  Yare ;  but  has  not  been  detected  either  in  Ireland  or 
Scotland,  though  several  gravel  and  clay  deposits  in  the 
latter  country  may  yet  be  discovered  to  belong  to  the  same 
era.  It  occurs  interestingly  developed  near  Paris;  trends 
along  the  north  coast  of  France,  Belgium,  Westphalia, 
Holstein,  and  Jutland,  in  apparent  connexion  with  the 
German  Ocean;  spreads  over  the  level  tract  lying  between 
the  Baltic  and  Northern  Ocean  in  Russia ;  and  occupies 
the  greater  portion  of  the  central  flats  which  lie  between 
the  Baltic  and  Black  seas.  Besides  these  expanses,  there 


678.  Why  are  the  localities  of  this  system  still  unsettled  ? 

679.  What  geological  reasoning  is  here  ? 


TFKFIAKY  STRATA.  101 

are  many  secluded  patches  along  the  valleys  of  the  Rhone 
and  Danube,  the  Swiss  hikes,  and  the  Italian  shores  of  the 
Mediterranean.  The  system  has  also  been  detected  along 
the  southern  basis  of  the  Himmalehs,  and  in  several  of  the 
North  American  valleys;  and  when  geological  research  has 
been  farther  extended,  there  is  little  doubt  of  its  being  dis- 
covered in  other  quarters  of  the  world.  In  speaking  of  the 
extent  of  country  occupied  by  deposits  of  incoherent  sands, 
marls,  and  clays,  like  those  of  the  tertiary  epoch,  it  must  be 
borne  in  mind  how  much  more  waste  they  would  suffer  by 
denudation  than  the  older  and  more  consolidated  strata. 
No  doubt  every  rock  system,  on  its  being  elevated  into  dry 
land,  must  have  suffered  diminution  by  denuding  causes; 
but  most  of  all  those  whose  materials  are  loosely  aggregated 
like  the  strata  now  under  icview. 

243.  Igneous  rocks  are  not  found  in  connexion  with  the 
tertiaries  of  England,  though  subterranean  movements  have 
thrown  them  into  anticlinal  ridges  and  basin-shaped  hol- 
lows. In  the  south  of  Europe  the  case  is  otherwise,  and 
the  geologist  finds  in  the  igneous  discharges  of  Auvergne, 
Switzerland,  the  Rhine,  Hungary,  and  Italy,  a  link  which 
connects  the  traps  of  the  secondary  period  with  the  pro- 
ducts of  recent  and  active  volcanoes.  According  to  JV1.  de 
Beaumont  the  western  Alps  (fi  -n  the  Mediterranean  to 
Mont  Blanc)  were  upheaved  dur.  g  this  era ;  and  the 
eastern  range  i»  supposed  to  be  of  suli  more  recent  origin, 
or  at  all  events  not  to  have  been  upraised  till  after  the  de- 
position of  all  the  tertiary  strata.  Along  the  Rhine,  in 
Hungary,  and  in  central  France,  the  igneous  elevations 
assume  a  more  diminutive  aspect — those  of  Auvergne  never 
arranging  themselves  in  a  continuous  axis,  but  presenting 
a  congeries  of  conical  crateriform  hills  of  no  great  altitude. 
In  their  composition,  these  igneous  rocks  are  chiefly  tra- 
chytic — passing  from  a  pretty  compact  grayish  felspathic 
mass  to  scoriaceous  tufa ;  but  in  no  case  presenting  the 
dark  bituminous  aspect  of  the  coal-measure  traps,  nor  the 

6^0.  What  of  igneous  rocks  and  volcanic  discharges? 
681.  What  is  the  nature  of  these  igneous  rocks  ? 


19*2  GEOLOGY. 

amygdaloidal  and  porphyritic  texture  of  those  associated 
with  the  old  red  sandstone. 

244.  Respecting  the  geographical  aspect  of  tertiary  dis- 
tricts, the  general  absence  of  igneous  rocks  would  indicate 
a  level  and  somewhat  unvaried  scenery;    and  this  is  the 
feature  which  prevails  in  the  wide  tertiary  plains  of  northern 
and  middle  Europe.     In  England  the  strata  partake  of  the 
undulations  of-  the  subjacent  chalk,  principally  developed, 
however,  in  the  flatish  basins  of  London  and   Hampshire. 
From   the  open   and   porous  character  of  the  sands  arid 
gravels,  tertiary  soils  are  in  general  light  and  dry,  capable 
of  profitable  cultivation,  but  by  no  means  naturally  fertile. 
The  hills  and  vine-growing  slopes  of  Auvergne  can  scarcely 
be  considered  as  reposing  on  a  tertiary  basis  any  more  than 
the  snow-clad  crags  and  peaks  of  the  Alpine  range,  both  of 
which  form  decided  exceptions  to  the  general  rule. 

245.  The  organic  remains  of  the  system  constitute   its 
most  important   and   interesting  feature.     The  ibssils  of 
earlier  periods  presented   little  analogy,  often  no  resem- 
blance, to  existing  plants  and  animals;  here,  however,  the 
similitude  is  frequently  so  complete,  that  the  naturalist  can 
scarcely  point  out  a  distinction  between  them  and  living 
races.     Geology  thus  unfolds  a  beautiful  gradation  of  being 
from  the  corals,  molluscs,  and  simple  Crustacea  of  the  grau- 
wacke — the  enamelled  fishes,  crinoidea,  and  cryptogamic 
plants  of  the  lower  secondary — the  chambered  shells,  sau- 
roid  reptiles,  and  marsupial  mammalia  of  the  upper  second- 
ary— up  to  the  true  dicotyledonous  trees,  birds,  and  gigantic 
quadrupeds  of  the  tertiary  epoch.     The  student  must  riot, 
however,  suppose  that  the  fossils  of  this  era  bring  him  up 
to  the  present  point  of  organic  nature,  for  thousands  of 
species  which  then  lived  and  flourished  became  in  their 
turn  extinct,  and  were  succeeded   by  others  long  before 
man  was  placed  on  the  earth  as  the  head  of  animated  exist- 
ence.    Of  Plants,  few  marine  species  have  been  detected ; 


682.  Flow  is  its  physical  geography  ? 

683.  What  of  the  organic  remains  ? 

684.  What  geological  reasoning  is  hazarded  here  1 


»  TERTIARY   STRATA.  193 

but  the  fresh-water  beds  have  yielded  cycadese,  conifers, 
palms,  wiliows,  elms,  and  other  species,  exhibiting  the  (rue 
dicotyledonous  structure.  Nuts  allied  to  those  of  the  cocoa 
and  other  palms  have  been  discovered  in  the  London  clay; 
and  seeds  of  the  fresh-water  characea,  or  stoneworts,  known 
by  the  name  of  gyrgonifes  (Gr.,  gyros,  curved,  and  gonos, 
seed),  are  common  in  the  same  deposit.  Of  the  Radiata, 
Articuluta,  and  Mollusca,  so  many  belong  to  existing  genera, 
that  the  circumstance  has  suggested  a  classification  of  ter- 
tiary rocks  according  to  the  number  of  recent  species  which 
they  contain.  Thus,  if  out  of  100  fossil  shells  5$0  should 
belong  to  recent  species,  the  deposit  in  which  they  are  im- 
bedded is  presumed  to  be  of  later  origin  than  one  from 
which  only  10  per  cent,  of  recent  shells  can  be  obtained. 
Proceeding  upon  this  plan,  M.  Deshayes  and  Mr.  Lyell 
arrange  the  entire  system  into  ihe  following  groups,  as  fur- 
ther explained  in  note,  page  96-7  : — 

PLEISTOCENE — Sicilian  deposits,  with  9o  per  cent,  of  recent  species. 
PLEIOCENE — Italian  and  Crag  deposits,  with   41    per  cent,  of  recent 

species. 
MEIOCENE — Vienna,   Bordeaux,    Turin,   &c.    18  per   cent,  of  recent 

species. 
EOCENE — Paris,  London,  Belgium,  3£  per  cent  of  recent  species. 

From  the  above  per  centage  the  student  will  perceive,  with 
respect  to  the  marine  mollusca  of  the  tertiary  era,  that  they 
approach  existing  forms  too  nearly  to  require  any  particu- 
lar description. 

246.  The  vertebrate  animals  make  a  similar  approach  to, 
^r  recession  from,  existing  races  as  we  ascend  or  descend 
among  the  tertiary  strata.  "  The  Fishes"  says  M.  Agassiz, 
"are  sov  nearly  related  to  existing  forms,  that  it  is  often 
difficult,  considering  the  enormous  number  (above  8000) 
of  living  species,  and  the  imperfect  state  of  preservation  of 
the  fossils,  to  determine  exactly  their  specific  relations.  In 
general,  I  may  say  that  I  have  not  yet  found  a  single  species 
which  was  perfectly  identical  with  any  nmrine  existing  fish, 
except  the  little  species  which  is  found  in  nodules  of  clay, 
of  unkmwn  geological  age,  in  Greenland.  The  species 

6S5    What  of  the  groups  of  fossil  shells  ? 
6b6.  What  of  tishes,  reptiles,  and  birds  1 


194  GEOLOGY.  • 

of  the  Norfolk  crag,  of  the  upper  subapennine  formation, 
and  of  the  molasse,  are  mostly  referable  to  genera  common 
in  tropical  regions.  In  the  lower  tertiaries  of  Condon,  the 
basin  of  Paris,  and  Monte  Bolca,  at  least  a  third  of  the 
species  belong  to  genera  which  are  now  extinct."  As  with 
the  fishes,  so  with  the  Reptilia,  among  which  we  find,  for 
the  first  time  in  the  history  of  the  globe,  the  remains  of 
genuine  crocodiles,  snakes,  and  representatives  of  the  frog 
tribe;  besides  several  existing  genera  of  fresh-water  and 
marine  turtles.  The  *iurians  of  the  saliferous  and  oolitic 
eras  had  by  this  time  passed  away,  to  be  succeeded  by  the 
above-named  reptiles,  whose  forms  and  habits  seem  to  have 
been  more  in  accordance  with  the  altered  conditions  of 
external  nature.  Of  Birds,  eight  or  ten  species  have  been 
discovered  in  the  Paris  basin,  referable  to  the  genera — 
buzzard,  owl,  quail,  woodcock,  sea-lark,  curlew,  and  peli- 
can. (tSee  Appendix.) 

247.  The  mammalia  of  the  tertiary  strata  are  those  fos- 
sils which  have  most  attracted  the  attention  of  palaeontolo- 
gists ;  and  this  deservedly  so,  from  their  being  the  proto- 
types of  many  existing  species,  and  as  marking  the  dawn 
of  conditions  suited  to  the  Fauna  of  the  present  day.  Of 
these  ancient  forms,  between  fifty  and  sixty  species  have 
been  determined,  a  majority  of  which  belong  to  a  division 
of  the  order  Pachydcrmata,  now  only  represented  by  four 

living  species;  namely,  three 
tapirs,  and  the  daman  of  the 
Cape.  This  division  com- 
prehends most  of  the  tht- 
roid  animals,  now  so  fre- 
quently alluded  to  in  works 
on  geology,  of  which  the 

pa/fBotherium  (see  fig.)  was 
Form  of  Palaeotherium.  r  c     ,          v  &  '  , 

one  of  the  most  prevalent 

and  characteristic.  A  detailed  enumeration  of  the  mam- 
malia of  this  era  would  be  inconsistent  with  the  rudimentary 

687.  What  of  the  mammalia  ? 

688.  How  many  species  have  been  determined  7 

689.  Name  some  of  these. 

690.  Explain  the  diagrams. 


TERFIARY  STRATA  195 

nature  of  this  treatise ;  we  shall  therefore  merely  advert  to 
the  leading  orders  now  determined  by  the  most  eminent 
f  >ssil  anatomists.  Quadrumana  (four-handed,  or  monkey 
tribe),  one  or  two  species  from  the  eocene  beds  of  the  Eng- 
lish basins;  Marsvpialia  (pouch-nursing),  three  or  four 
species  of  a  diminutive  size;  Cheiroptera  (hand-winged), 
two  or  three  species  of  bat,  chiefly  from  the  gypsum  beds 
of  Montmartre  ;  Insectivora  (insect-eaters),  partial  remains 
of  a  species  of  mole ;  Carnivora  (flesh-devourers),  several 
species  have  been  determined  allied  to  the  bear,  hyaena, 
fox,  dog,  seal,  cat,  weasel,  &c.;  Rodentia  (gnawers),  ten 
or  twelve  species  allied  to  the  beaver,  rat,  hare,  lagomys, 


Restored  Form  of  Deinotherium. 

squirrel,  &c.;  Pachydtrmata  (thick-skinned),  many  genera 
and  species,  such  as  the  rnatstodon,  the  deinotherium  (see 
fig.),  elephant,  hippopotamus,  rhinoceros,  horse,  boar,  tapir, 
and  a  host  of  animals  allied  to  the  tapir;  Ruminantia  (cud- 
chewers),  a  few  species,  as  the  stag,  deer,  elk,  antelope, 
ox  (?),  &c.;  Cetacea  (whales),  one  or  two  species;  and 
gigantic  Edentata  (toothless  animals),  now  faintly  repre- 
sented by  the  sloth,  the  ant-eater,  and  the  diminutive  arma- 
dillo. (See  Appendix.) 

248.  Of  the  conditions  of  the  world  during  the  deposition 
of  the  tertiary  strata,  we  are  enabled  to  form  some  esti- 
mate from  the  nature  of  their  fossils,  and  from  the  peculiar 
composition  and  aggregation  of  their  rocky  materials.  So 
far  as  Europe  is  concerned,  part  of  the  existing  land  must 
have  been  then  elevated  above  the  waters,  forming  a  series 
of  insular  ranges,  with  flat  valleys  and  shallow  seas  between. 


691.  What  geological  reasoning  is  found  here  1 


196 

From  these  islands,  and  from  continents   now  submerged, 
rivers  of  considerable  extent  seem  to  have  borne  sand,  clay, 
and   vegetable  debris,  and   to  have  deposited  them  in  ihe 
seas  and  estuaries,  while  gravel,  flint  pebbles,  broken  corals, 
and  shells,  were  strewn  along  the  shore  by  ordinary  littoral 
influences.  Such  materials  would  give  rise  to  beds  of  sand, 
clay,  gravel,  lignite,  and  calcareous  conglomerate,  enclosing 
marine  remains,  with  others  of  fresh-water  and  terrestrial 
origin    brought  down  by  the  rivers.     But  several  tertiary 
basins  exhibit  strata  of  decided  fresh  water  origin,  alter- 
nating with  others  as  decidedly  marine;  and  to  account 
for  this  phenomenon,  we  must  have  recourse  to  another  set 
of  agents.     In  the  deltas  of  many  modern  rivers,  like  that 
of  the  Niger,  lagoons  of  fresh  water  are  frequently  cut  off 
from  connexion  either  with  the  branches  of  the  river  or 
with  the  ocean,  and  in  these  myriads  of  shell-fish,  aquatic 
plants,  crocodiles,  hippopotami,  and  other  fresh-water  and 
amphibious  races  abound.     At  some  subsequent  period  the 
connexion  with  the  ocean  is  renewed — there  being  in  gene- 
ral only  a  slight  eminence  of  mud  or  sand  to  separate  them 
— and  thus    the  succeeding   deposits  assume  a  character 
decidedly  marine.     By  these  means  it  is  easy  to  conceive 
how    alternations    of  marine  and  fresh-water  strata  would 
occur:  and  particularly  when   we  know  that  the  south  of 
Europe  (central  France  and  the  Alps)  was,  during  the  ter- 
tiary era,    subjected   to    extensive    volcanic  disturbances, 
which  would  give  rise  to  frequent  submergences  and  ele- 
vations.    We  are  thus  enabled  to  account  for  the  composi- 
tion  and  aggregation  of  the  tertiary  strata ;  and  when  we 
reflect  on  their  comparatively  recent  origin,  and  the  fact 
that  they  are  in  many  places  not  overlaid  by  other  material, 
there  is  no  difficulty  in  perceiving  how  they  should  be  so 
loose  and  incoherent  in   their   texture.     Again,  when  we 
look  at  the  nature  of  their  fossils,  we  are  led  to  associate 
with  them  ideas  of  a  warm  arid  genial  climate.     The  lands 
which    furnished    the   cycadea?,   palms,   cocoa    nuts,   and 
monkeys  of  the  English  tertiaries,  and  the  mastodons,  ele- 
phants, rhinoceroses,  hippopotami,  crocodiles,  and  turtles 
of  the  Paris  basin,  must  have  enjoyed  a  temperature  similar 
to  i hat  of  the  present  tropics.     The  beds  of  lignite  bear 


TI.RTIAHV   STRATA. 


107 


evidence  of  a  luxuriant  vegetation  for  the  support  of  so 
many  huge  graminivora ;  while  the  presence  of  birds,  in- 
sects, and  the  higher  orders  of  mammalia,  point  to  atmo- 
spheric and  other  vital  conditions  little  different  from  those 
now  existing.  In  fact,  we  find  in  the  deltas  of  the  Ganges 
and  Niger — in  their  jungles,  lagoons,  and  swamps — in 
their  elephants,  hippopotami,  and  crocodiles — almost  perfect 
analogies  to  those  estuaries  and  shallow  seas  in  which  the 
tertiary  strata  of  Europe  were  deposited. 

249.  In  an  economical  point  of  view,  the  tertiary  strata 
are  of  considerable  local  importance.  The  celebrated  burr 
millstones  of  France,  are  obtained  from  the  upper  fresh- 
water siliceous  limestones  of  the  Paris  basin;  some  of  the 
strata  of  which  also  furnish  marble  capable  of  receiving  a 
high  polish.  Marked  by  the  numerous  shells  which  are  im- 
bedded in  it,  this  marble  is  by  no  means  unnrnamental,  and 
has  been  used  in  the  construction  of  the  jets  deau  in  the 
galleries  of  the  Tuilleries.  Many  of  the  fresh-water  lime- 
stones rapidly  disintegrate  on  exposure  to  air  and  moisture, 
and,  falling  down  to  the  state  of  marl,  are  used  as  manure; 
while  the  "  crag"  is  occasionally  so  calcareous,  as  to  serve 
the  ordinary  purposes  <;f  limestone.  Pipe  and  potters' 
clay  are  extensively  obtained  both  from  the  London  and 
Paris  basins ;  the  term  plastic,  applied  to  the  lower  beds, 
being  derived  from  the  circumstance  of  the  clay  readily 
receiving  the  mould  or  form  of  the  potter  (Gr.  plasso, 
I  form).  Gypsum  (sulphate  of  lime)  is  perhaps  the  most 
valuable  member  of  the  deposit ;  it  is  found  abundantly  in 
the  Paris  basin,  and  when  calcined,  reduced  to  powder  and 
kneaded  with  water,  forms  the  well  known  plaster  of  Paris 
so  extensively  used  by  image-makers,  plasterers,  stereotype- 
founders,  and  others.  Gypsurn  has  also  been  recently  ap- 
plied as  a  topdressing  to  crops,  and  as  a  fixer  of  the  vola- 
tile principles  of  organic  manures.  Lignite  (Lat.,  lignum, 
wood),  or  wood-coal,  is  found  in  some  tertiary  districts,  the 
o.ily  deposit  of  importance  in  England  being  that  of  Bovey 
Hayfield,  near  Exeter.  Amber  frequently  occurs  with 


692.  Whit  are  the  economical  uses  of  the  system  T 

693.  Wh.ch  is  the  mosf  valuable  product  ? 

9* 


133  •         GEOLOGY. 

these  lignitip  beds,  and  appears  to  have  been  a  gum  or  gum- 
resin  exuded  by  the  trees  with  which  it  is  associated, 

EXPLANATORY   NOTE. 

THEROID  ANIMALS. — The  termination  therium  (Gr.  therion,  a  wild 
beast)  is  adopted  in  geology  to  designate  certain  classes  of  fossil  mam- 
malia, whose  structure  and  habits  have  not  yet  been  fully  established 
by  anatomists.  The  individual  animals  are  characterized  by  a  prefix 
which  applies  to  some  peculiarity  of  form,  the  place  where  found,  or 
the  name  of  the  discoverer.  Thus  we  have  the  (temotherium  (terrible 
wild  beast) ;  the  palteotherium  (ancient) ;  the  anop/otherium  (unarmed, 
having  no  weapons  of  defence) ;  the  Wtfg'atherium  (great)  ;  the  elasmo- 
therium  (from  the  laminated  structure  of  its  teeth) ;  the  anthraco- 
therium  (found  in  the  lignitic  beds)  ;  the  ceu'notherium  (recent) ;  the 
s/t?atherium  (found  in  the  Sivalic  range  of  the  Himmalehs) ;  &c. 
Though  most  of  these  animals  are  found  in  tertiary  deposits,  it  would 
appear  that  some,  such  as  the  megatherium,  outlived  that  era,  and 
continued  inhabitants  of  the  globe  long  after  the  commencement  of 
the  current  epoch. 

SUPERFICIAL  ACCUMULATIONS. 

250.  After  the  deposition  of  the  Tertiary  Strata,  a 
great  change  took  place  in  the  relative  distribution  of  land 
and  ocean.  Most  parts  of  Europe,  America,  and  the  other 
continents  were  elevated  above  the  waters ;  other  regions 
seem  to  have  been  submerged,  and  an  arrangement  of 
physical  conditions  established  not  differing  widely  from 
those  now  existing.  But  these  new  conditions  did  not  for 
an  instant  arrest  the  degrading  and  transporting  power  of 
water,  the  wasting  effects  of  the  atmosphere,  the  disturbing 
efforts  of  volcanoes,  or  the  progressive  development  of 
organic  life :  the  same  agents  which  had  exerted  them- 
selves from  the  beginning  of  time,  in  modifying  the  physical 
features  of  the  world,  continued  their  career,  only  differing 
in,  power  and  degree  according  to  this  new  arrangement. 
Thus,  accumulations  of  sand,  gravel,  clay,  vegetable  and 
animal  matter  took  place  above  the  previously  deposited 
strata — every  river,  lake,  sea  shore,  shell-bed,  coral-reef, 
and  peat-moss,  contributing  its  peculiar  quota.  It  is  to 

694.  Define  theroid. 

695.  Define  the  terms  in  the  note. 

696.  What  system  is  here  considered? 

697.  How  are  these  recent  and  progressive  formations  explained? 


SUPERFICIAL  ACCUMULATIONS.  l!)9 

such  recent  and  progressive  formations,  now  occupying  the 
surface  of  the  earth's  crust,  that  the  attention  of  the  student 
is  here  directed. 

251.  The  term  "Superficial  A ccunudations"  is  applied 
to  these  loosely-aggregated  masses  of  matter — whatever  be 
tfieir  composition  or  mode  of  formation — to  distinguish 
them  from  the  tertiary  sands  and  clays,  in  all  of  which 
stratification  is  distinct  and  undeniable.  Other  designa- 
tions have  been  proposed,  such  as  post-tertiary  (atler- 
trrtiary),  quaternary  (fourth  system),  &c. :  but  that  which 
we  have  chosen  merely  indicates  their  position,  leaving 
further  subdivisions  to  be  made  in  the*  course  of  description. 
The  most  natural  division  is  that  which  attempts  to  arrange 
these  accumulations  according  to  the  respective  dates  of 
their  formation.  Thus: — 

1    Deposits  now  in  progress,  and  depending  upon  ordinary  causes. 

2.  Those  whose  origin  depended  upon  ordinary  causes  now  dormant. 

3.  Those  which  owe  their  origin  to  extraordinary  causes  now  dormant. 

A  classification  of  this  kind,  however,  is  attended  with  so 
many  difficulties,  that  it  is  next  to  impossible  to  adopt  it 
with  any  degree  of  accuracy.  For  instance,  it  is  often 
very  difficult  to  distinguish  the  gravel  of  some  ancient  lake, 
containing  bones  of  the  stag,  elk,  and  elephant,  from  true 
tertiary  strata;  and  who  shall  decide  whether  certain  inland 
ranges  of  sand  and  gravel  arose  from  extraordinary  or 
ordinary  causes?  Again,  in  many  valleys  alluvial  matter 
has  been  accumulating  from  the  time  that  they  received  their 
existing  configuration  up  to  the  present  day,  thus  making 
the  most  ancient  and  most  recent  of  such  deposits  depend 
upon  one  long-continued  and  progressive  agency.  Further, 
an  iceberg  laden  with  rock  debris  and  boulders,  strewing 
its  burden,  as  it  melts  away,  along  the  bed  of  the  ocean,  is 
an  ordinary  operation;  yet  were  the  bottom  of  the  sea, 
with  its  mud,  gravel,  and  immense  boulders,  to  be  elevated 
into  dry  land,  appearances  would  present  themselves  which 
geologists  would  be  very  apt  to  ascribe  to  violent  and 

698.  Define  their  peculiarities. 

699.  Which  is  the  most  natural  division  T 

700.  What  objections  to  this  are  stated  T 


200 


GEOLOGY, 


unusual  operations  of  water.  Under  these  circumstances, 
the  more  philosophical  mode  of  treating  the  Superficial 
Accumulations  will  be  to  adopt  no  classification  which  in- 
volves either  the  time,  the  ordinary  or  extraordinary  cause 
of  their  formation ;  but  simply  to  treat  them  in  succession 
according  to  their  composition,  or  the  agents  obviously 
employed  in  their  deposition.  Following  out  this  view,  the 
principal  agencies  and  their  results  may  be  arranged  as 
under: — 


Agencies. 
DETRITAL. 

MARINE. 

FLUVTATILE. 

* 
LACUSTRINE. 


MINERAL 

AND 
CHEMICAL. 


ORGANIC. 


VOLCANIC. 


Nature  of  Accumulations. 

(  Erratic  blocks  or  boulders  ;  dark  tenacious  clays. 
<Ossiferous  gravels,  sands,  and  pebbly  clays. 
(Ossiferous  caves,  fissures,  and  breccia. 
(  Raised  or  ancient  beaches  ;  submarine  forests. 
<  Marine  silt,  sand-drift,  shingle  beaches,  &c. 
(  Submarine  deposits  and  accumulations. 
Terraces  on  valley  sides,  marking  successive  water- 
levels. 
Valley  deposits,    consisting   of  river  sand,  gravel, 

silt,  &c. 

Deltoid  or  estuary  deposits,  ancient  and  progressive. 
Sites   of  ancient  lakes  now  silted  up  with  various 

debris. 

Marls,  such  as  shell,  clay,  and  calcareous  marls. 
Lacustrine  silt,  and  accumulations  now  in  progress. 
Calcareous — calc-tuff,  sinter,  travertine,  stalactites, 

and  stalagmites. 
Siliceous  and  aluminous  deposits  from  springs,  &c. 
Saline  and  sulphurous  deposits  from  springs,  from 

the  sea,  volcanoes,  &c. 
Bituminous  exudations,  pitch  lakes,  &c. 
Vegetable — peat-mosses,  jungles,  vegetable  drift. 
Animal — shell-beds,  coral-reefs,  &c. 
S  Soils — primitive  earths,  with  admixtures  of  organ- 
l      ized  matter. 

(Earthquakes — elevations     and     depressions,    &c., 
j      caused  by 

J  Volcanoes — elevations,     disruptions,      and     other 
"A      changes  caused  by 

I  Discharges  and  accumulations  of  lava,  scoriae,  dust, 
I    &c. 


The  above  synopsis  comprises  all  masses  of  matter  which 
produce  any  sensible  modification  of  the  earth's  surface 

701.  Explain  the  tabular  arrangement. 

702.  What  of  the  organic  and   volcanic  agencies  T 


ERRATIC  BLOCK,  OR  HOCLDER,  GROUP.        201 


other  accumulations  than  these  must  be  of  a  very  local  and 
limited  description. 

ERRATIC  BLOCK,  OR  BOULDER,  GROUP. 

252.  The  terms  "  erratic  block  group"  "  boulder  forma- 
tion" "diluvium"  and  " diluvial  drift"  are  indiscrimi- 
nately given  by  geologists  to  a  thick  mass  of  dark  tenacious 
clay  which  overlies  extensive  districts,  intermingled  with 
numerous  boulders  having  a  rounded  and  water-worn  ap- 
pearance. There  is  nothing  like  regularity  of  deposit  in 
this  formation,  unless  it  may  be  said  that  it  attains  the 
greatest  thickness  and  uniformity  of  composition  on  exten- 
sive plateaus  like  those  of  the  coal  measures,  at  the. eastern 
extremity  of  certain  valleys,  and  on  the  south-eastern  flank 
of  hills  belonging  to  the  secondary  period.  The  clay  is 
generally  of  a  dark  blue  colour,  though  in  some  localities 
it  assumes  a  reddish  hue.  There  are  no  lines  of  lamina- 
tion in  the  mass,  and  no  appearances  of  stratification,  unless 
in  some  districts  where  there  is  a  sort  of  natural  division 
into  "  upper  and  lower  clays" — the  lower  being  dark  and 
more  compact,  the  upper  lighter  in  the  hue,  and  separated 
from  the  other  by  a  thin  reddish  streak.  Waiving  these 
minutiae,  the  whole  may  be  described  as  a  covering  of  com- 
pact dark  clay,  from  10  to  120  feet  in  thickness,  full  of 
boulders  and  rolled  stones  from  the  size  of  an  egg  to  many 
tons  in  weight;  these  blocks  occupying  the  bottom,  middle, 
or  surface  of  the  mass,  without  regard  to  gravity  or  any 
other  law  of  arrangement.  The  boulders  are  of  granite, 
syenite,  primitive  greenstone,  gneiss,  mica  schist,  and  other 
crystalline  rocks  of  a  hard  and  durable  texture.  Limestone 
blocks  are  of  very  rare  occurrence,  and  the  more  friable 
rocks  of  the  upper  formations  are  seldom  or  ever  to  be 
met  with.  This  clay,  with  its  intermingled  boulders,  gene- 
rally rests  upon  the  denuded  outcrops  or  edges  of  the  rock 
formations;  is  sometimes  underlaid  by  masses  of  gravel; 
and  not  unfrequeritly  contains  "  nests,"  or  irregular  patches 
of  rounded  pebbles. 

703.  By  what  names  is  the  next  group  called  T 

704.  Of  what  materials  do  the  boulders  consist  T 

705.  What  are  the  peculiarities  of  this  clay. 


202  GEOLOGY. 

253.  Besides  these  patches  which  are  interwoven  with  the 
clay,  there  are  independent  accumulations  of  gravel,  anu 
rubbly  masses  of  rock-fragments,  which  seem  to  have  been 
formed  contemporaneously  with  the  boulder-clay,  and  by 
the  same  agency.    In  Britain  such  accumulations  generally 
occupy  the  eastern  extremity  of  longitudinal  valleys,  where 
they  form  curious  ranges  of  flat-topped  hillocks;  abut  against 
the  base  of  some  mountain ;  or  gather,  without  regard  to 
any  order  of  arrangement,  along  the  eastern  flank  of  those 
trap  hills  which  present  a  bold  front  or  "  crag"  to  the  west- 
ward.    They  are  found   for  the  most  part  in  more  open 
situations  than  the  clay,  as  if  they  had  been  arrested  in  their 
progress  eastward  by  prominences  and  shallows,  while  the 
clays  were  borne  to  deeper  and  rr.ore  sheltered  recesses. 
Like  the  dark  clays,  they  are  destitute  of  organic  remains, 
their  larger  pebbles  are  derived  from  primitive  rocks,  inter- 
spersed with  fragments  of  sandstone,  shale,  and  coal  from 
the  secondary  formations. 

254.  To  account  for  the  origin  of  the  group  thus  described, 
many  theories  have  from  time  to  time  been  advanced,  of 
which  only  two  deserve  notice,  as  being  at  all  adequate  to 
the  purpose  intended.     The  first  is  that  which  supposes 
a  set  of  powerful  currents  to  have  passed  over  Britain  and 
the  adjoining  continent;    these  currents  taking  a  course 
from  the  north  arid  north-west  towards  the  south  and  south- 
east, and  sweeping  before  them  clay,  sand,  gravel,  and  loose 
blocks,  which  were  deposited,  as  the  force  of  the  waters 
abated,  without  any  order  or  arrangement.     How  long  the 
currents  continued,  theorists  do  not  aver;    but  from    the 
water-worn  aspect  of  the  boulders  and  gravel,  an  indefinite 
period  is  allowed.     With  respect  to  the  direction  of  the 
drifting  force,  little  doubt  is  entertained,  for  many  reasons: 
—  1.  Blocks  of  granite,  gneiss,  &/c.  which  must  have  been 
derived  from  the  Grampians,  are  found  scattered  along  the 
eastern  lowlands  of  Scotland;    primitive  rocks   from   the 
Lammermuir  and  Cheviot  ranges  are  detected  in  the  vale 

706.  What  vaiiety  of  accumulations  are  found  here? 

707.  What  is  the  first  theory  broached  ? 

708.  What  proofs  of  aqueous  agency  are  manifest? 

709.  Whence  did  the  currants  flow  ? 


ERRATIC  BLOCK,  OR  BOULDER,  GROUP.        203 

of  the  Tweed  and  in  Northumberland ;  others  from  the 
Cumberland  mountains  are  widely  dispersed  over^Durhaui 
and  the  east  of  Yorkshire ;  boulders  from  the  Welsh  range 
are  found  in  the  midland  counties  of  England  ;  while  the 
erratic  blocks  of  Friesland  and  Germany  point  to  the  Scan- 
dinavian ridge  as  the  source  from  which  they  were  derived. 
2.  Those  hills  which  range  east  and  west  have,  without  ex- 
ception, their  western  brows  swept  bare,  while  their  eastern 
flanks  are  thickly  strewed  with  gravel  and  boulders.  3. 
Many  accumulations  of  gravel  bear  evidence  of  their  having 
been  piled  up  by  a  force  from  the  north-west.  4.  Blocks  evi- 
dently derived  from  the  outcrops  of  certain  strata  are  often 
fouud  among  the  debris  a  few  yards  to  the  south-east,  show- 
ing clearly  that  the  transporting  power  passed  over  them 
from  the  north-west.  5.  The  supposed  currents  have  been 
modified  in  their  direction  by  ranges  of  hills,  so  as  to  set 
the  volume  of  water  with  greater  rapidity  down  the  valleys 
which  lie  between  them,  as  the  greatest  accumulations  of 
drill  and  b  >ulders  are  found  at  the  eastern  extremities  of 
such  gorges  and  valleys.  But  while  no  doubt  is  entertained 
either  as  to  the  agency  of  water  in  the  formation  of  these 
accumulations,  or  as  to  the  direction  in  which  the  waters 
flowed,  great  difficulty  is  felt  in  conceiving  any  current 
sufficiently  powerful  to  sweep  be  fore  it  blocks  of  several 
tons  weight,  and  that  over  heights  and  hollows  for  many 
hundred-;  of  miles.  Indeed  it  seems  impossible  to  recon- 
cile the  theory  of  violent  currents  with  the  phenomena  pre- 
sented; for,  granting  the  occurrence  of  some  extraordinary 
cataclysm,  during  which  the  waters  of  the  ocean  were 
thrown  over  the  land,  the  currents  must  have  abated  in 
velocity  as  they  drew  to  a  close,  leaving  the  detritus  to 
arrange  itself  more  in  accordance  with  the  laws  of  gravity 
than  what  is  exhibited  in  a  mass  of  clay  and  boulders. 

2-55.  Tke  second  theory  supposes  that  those  portions  of 
Europe  now  covered  with  erratic  blocks  were  submerged 
after  the  deposition  of  the  stratified  formations ;  thai  tins 
submergence  was  caused  by  some  extraordinary  revolution 


710.  What  difficulties  are  sUted  ? 

711.  What  other  theory  is  stated  T 


204  GEOLOGY. 

in  the  planetary  relations  of  our  earth  ;  that  it  was  accom- 
panied by  a  change  of  climate,  and  other  terrestrial  condi- 
tions; ttfat  while  in  this  state,  icebergs  and  avalanches 
formed  around  the  earlier  mountains  which  were  still  left 
above  water ;  and  that  these  icebergs,  as  they  were  loosened 
from  the  shore  by  the  heat  of  summer,  and  floated  south- 
ward by  the  currents  of  the  ocean,  dropped  their  burden  of 
boulders  and  gravel  precisely  as  Captain  Scoresby  (page  34) 
found  modern  icebergs  dropping  their  debris  in  the  northern 
seas,  and  as  the  officers  of  the  recent  Antarctic  expedition 
observed  similar  phenomena  in  the  Southern  Polar  Ocean. 
It  is  further  supposed, .that  while  icebergs  distributed  the 
erratic  blocks  and  other  debris  in  d.ep  waters,  avalanches 
and  glaciers  were  forming  moraines  of  gravel  in  the  valleys 
of  the  then  existing  land  analogous  to  what  is  observed  in 
the  alpine  glens  of  Switzerland.  Again,  one  cannot  read 
Mr.  Simpson's  account  of  the  shores  of  the  Polar  seas,  and 
learn  that  the  ice  formed  during  winter  over  whole  leagues 
of  gravel,  breaks  up  during  summer,  and  i»  blown  on  the 
beach  by  winds,  or  piled  up  by  the  tides,  where,  melting,  it 
leaves  long  flat-topped  ridges,  without  perceiving  a  won- 
derful resemblance  between  these  effects  and  the  long 
singularly-shaped  ridges  of  "  diluvial"  gravel.  According 
to  this  theory,  it  is  easy  to  account  for  the  south-eastward 
direction  of  the  drift,  for  the  Polar  Ocean  still  maintains  its 
great  southward  current  to  the  equatorial  seas,  modified, 
undoubtedly,  in  its  course,  by  the  inequalities  of  the  bot- 
tom over  which  it  passes.  The  chief  difficulty  to  be  obvi- 
ated is  the  temporary  diminution  of  temperature  which  the 
north  of  Europe  must  have  then  experienced  ;  and  this  can 
only  be  accounted  for  by  some  derangement  in  the  plane- 
tary relations  of  our  globe. 

256.  Both  theories  art  beset  with  many  difficulties,  and 
though  the  latter  accounts  more  satisfactorily  for  most  of 
the  phenomena  of  the  erratic  block  group,  still  there  are 
many  points  respecting  the  distribution  and  extent  of  the 
deposit  to  be  investigated  before  either  can  be  finally 


712.  What  of  icebergs  ? 

"13.   How  is  the  only  difficulty  obviated  t 


OSSIFEUOUS  SANDS   AND   (i  RAVEL.  205 

adopted.  All  that  can  be  affirmed  in  the  present  state  of 
the  science  is  the  composition  arid  nature  of  the  clay,  gravel, 
and  boulders,  as  above-described — the  course  of  the  cur- 
rents concerned  in  their  deposition — the  fact  of  the  land 
having  a  configuration  of  hill  and  valley  not  differing  much 
from  what  now  exists — and  the  peculiar  scantiness,  if  not 
total  absence,  of  organic  remains.  If  the  latter  theory  be 
adopted,  it  is  easy  to  perceive  how  the  soft  bottom  of  the 
ocean,  as  it  was  elevated  into  dry  land,  would  be  furrowed 
and  channeled  by  the  receding  waters — here  being  swept 
bnre  of  its  mud,  but  retaining  the  boulders;  there  being 
covered  by  accumulations  of  transportable  clay  and  gravel ; 
while  the  deeper  hollows  being  left  undrained,  would  form 
lakes  and  morasses,  which  were  in  turn  to  be  silted  up  by 
subsequent  material. 

OSSIFEROUS    SANDS    AND    GRAVEL. 

257.  Next  in  point  of  antiquity  to,  if  not  contemporaneous 
with,  the  clays  and  boulders  of  the  preceding' group,  may  be 
ranked  those  ossiferous  sands  and  gravels  found  scattered 
at  intervals  over  the  valleys  of  Britain,  the  continent  of 
Europe,  and  the  river  plains  of  North  America.  They  are 
termed  ossif trout  (Lat.,  os,  a  bone,  and  fero,  1  bear),  from 
their  containing  bones  of  elephants,  hippopotami,  horses, 
bears,  deer,  and  other  animals,  which  belong  to  existing 
species,  but  do  not  now  inhabit  the  regions  where  these 
remains  occur.  For  instance,  large  portions  of  England, 
Wales,  Scotland,  and  Ireland  are  covered  by  irregular  accu- 
mulations of  rounded  pebbles  and  gravelly  sands,  in  which 
are  found  bones  of  the  elephant,  hippopotamus,  &c.,  none  of 
which  have  been  known  in  this  country  within  the  historic 
period.  In  similar  deposits  the  skeletons  of  elephants  and 
mammoths  have  been  discovered  in  Siberia  and  the  north 
of  Europe;  the  bones  of  the  mammoth,  mastodon,  and 
megatherium  in  America  ;  and  even  among  the  Esquimaux 

714.  What  is  supposed  to  be  ascertained? 

715.  What  of  ossiferous  sands  and  gravel  I 

716.  Why  so  named  ? 

717.  Where  are  they  found  ? 


TY 


Y 

m. 


20(5 


GFOLOOV. 


of  the  Polar  seas  Captain  Ross  and  Mr.  Simpson  observed 
platters  fashioned  from  the  fossil  grinders  of  these  gigantic 
mammalia.  Neither  at  present,  nor  throughout  the  whole 
historic  period  of  four  thousand  years,  have  any  of  those 
countries  been  in  conditions  of  climate  to  support  such 
huge  graminivora,  .and  therefore  geologists  are  compelled 
to  assign  a  very  remote  and  ancient  origin  to  the  gravels  in 
which  their  relics  are  entombed. 


Scale  of 

Skeleton  of  Megatherium. 

258.  The  composition  and  aggregation  of  these  sands  »<&• 
gravels  point  to  the   long-continued  action   of  water  bt 

7 IS.  Whv  have  ^eolopists  assigned  remote  antiquity  to  these  ? 
7)9    What  proof  of  aqueous  agency  here  ? 


OSS1FEROUS  SAVDS  AND  C7RAVFL.  2!)7 

which  their  pebbles  were  rounded  and  smoothed  like  those 
of  the  rivers,  lakes,  and  sea-shores  of  the  present  day.  The 
mineral  character  of  the  pebbles  enables  the  geologist  often 
to  decide  with  certainty  as  to  the  quarter  from  whence 
they  were  drifted  ;  and  in  Britain  this  generally  corresponds 
\vith  that  from  which  the  erratic  blocks  were  derived.  Like 
the  boulders,  the  great  mass  of  the  pebbles  are  from  primi- 
tive rocks,  interspersed  with  secondary  sands,  rolled  flints, 
and  calcareous  cement.  The  imbedded  bones  are  more 
or  less  impregnated  with  iron  and  lime,  are  harder  and 
heavier  than  recent  bone,  but  never  so  much  petrified  as  to 
obliterate  the  bony  structure.  The  gravels  have  all  a  light 
ferruginous  tint,  and  can  only  be  distinguished  in  certain 
localities  from  true  tertiary  gravel  by  the  recentn^ss  of  their 
fossils,  or  by  some  circumstance  of  position  or  mode  of 
aggregation. 

259.  Ah/eh  lihcertainty  prevails  with  respect  to  the  origin 
and  aggregation  of  these  ossiferous  sands  and  gravels. 
Many  of  them  are  no  doubt  local,  and  have  been  formed 
by  the  action  of  rivers,  the  silting  up  of  lakes  and  other 
extensive  shallows;  and  could  such  be  separated  from  those 
which  appear  to  have  been  accumulated  by  some  very 
powerful  and  extensive  agency,  the  task  were  greatly  sim- 
plified. Unluckily,  however,  this  seems  to  remain  an 
insuperable  difficulty,  so  that  geologists  are  compelled  to 
class  together  all  deposits  of  ancient  ossiferous  gravel  into 
one  group,  without  much  regard  to  the  agencies  concerned 
in  their  accumulation.  This  grouping  is  rendered  still 
more  indefinite  by  the  assertion  of  some  eminent  geolo- 
gists, that  ossiferous  gravels'have  been  found  underneath 
the  erratic  boulder  clay,  containing  the  same  kind  of  bones 
with  those  above  it.  Should  this  be  the  case,  it  would 
tend  to  establish  the  theory,  that  the  ossiferous  gravels  and 
erratic  blocks  look  their  origin  from  the  same  set  of  un- 
usual causes;  that  they  belonged  to  an  era  which  was 
posterior  to  the  tertiary,  and  prior  to  the  existing  arrange- 
ments of  nature;  and  that  before  this  epoch,  which  was 

720.  What  peculiarities  are  named  ? 

721.  What  theories  of  their  origin  and  aggregation  7 


208  GEOLOGY. 

of  considerable  duration,  many  of  the  tertiary  races  had 
died  away,  and  been  succeeded  by  others,  most  of  which 
still  exist,  though  now  extinct  in  the  regions  where  they 
then  flourished. 

OSSIFEROUS    CAVES,    FISSURES,    AND    BRECCIA. 

260.  Belonging  to  the  same  era  with  the  ossiferous  gravels, 
and  only  here  separated  for  the  sake  of  perspicuity,  occur 
numerous  caverns  and  fissures  filled  with  the  bones  of  ele- 
phants, rhinoceroses,  hyaenas,  bears,  deers,  and  other  ani- 
mals.     These   caverns   are    found   in    England,    France, 
Belgium,  Germany,  along  the  coasts  of  the  Mediterranean, 
in  North  America,  and  in  Australia.     They  are  situated 
almost  exclusively  in  thick  strata  of  limestone,  a  rock  pecu- 
liarly liable  to  be  fissured  and  worn  out  by  the  action  of 
springs  and  subterranean  waters.    Among  the  mud  of  these 
ancient  caverns,  or  covered  over  with  calcareous  incrusta- 
tions, lie  the  bones  of  land  quadrupeds  perfectly  preserved, 
and  capable  of  being  compared  with  existing  races.    "  The 
result,"  says  Professor  Phillips,  "  is  extremely  remarkable: 
instead  of  a  large  proportion  of  the  existing  species  of  ani- 
mals, which,  during  the  early  periods  of  history,  if  not  in 
later  times,  might  have  been  expected  to  fall  into  fissures, 
retire  into  caves,  or  be  dragged  by  wolves  to  their  dens,  we 
find  the  greater  number  of  bones  to  belong  to  elephants, 
large  feline  animals,  the   rhinoceros,   hippopotamus,  elk, 
hyaena,   indiscriminately   entombed  with  oxen,  deer,  and 
many  smaller  animals."     Masses  of  bones 'are  also  found 
filling  fissures  and  other  openings  in  rocks,  mingled  with 
pebbles,  rnud,  fragments  of  shells,  &c.     To  such  accumu- 
lations the  term  osseous  breccia  is  applied,  from  the  frag- 
mentary nature  of  the  compound. 

261.  Tke  number  of  ossiferous  caverns  is  very  great,  but 
we  can  only  allude  to  those  which  occur  in  England.     In 
general  they  are  situated  on  the  limestone  escarpments  of 
the  secondary  hills,  or  on  the  terraced  side  of  some  valley. 
In  the  latter  case,  they  are  considerably  above  the  existing 

722.  Where  are  these  caverns  found  ? 

723.  What  peculiarities  characterize  these  ? 

724.  How  are  they  situated  in  England? 


OSSIFEROUS  CAVES,  FJSSURES,  AND  BRECCIA.  213 

bed  of  the  valley,  though  at  one  time  they  must  have  been 
on  a  level  with  the  waters  which  occupied  its  expanse. 
The  most  celebrated  are  Banwell  Cave  and  Hutton  Hole 
in  the  Mendip  hills,  Dream  Cavern  near  Wirksworth,  Peak 
Cavern  in  Nidderdale,  Rents  Hole  at  Torquay,  and  Kirk- 
dale  Cave  in  Yorkshire.  The  latter  has  been  thus  de- 
scribed:— "  Kirkdale  Cave  is  situated  about  twenty-five 
miles  north-east  of  Xprk,  above  the  northern  edge  of  the 
great  vale  of  Pickering,  and  thirty  feet  above  its  waters. 
Its  floor  is  upon  the  great  scale,  level  for  the  whole  length 
yet  explored  (250  feet),  and  nearly  conformable  to  the  plane 
of  stratification  of  the  coralline  oolite  in  which  it  occurs. 
In  some  parts  the  cave  is  three  or  four  feet  high,  and  roofed, 
as  well  as  floored,  by  the  level  beds  of  this  rock ;  in  other 
parts  its  height  is  augmented  by  open  fissures,  which  com- 
municate through  the  roof,  and  allow  a  man  to  stand  erect. 
The  breadth  varies  from  four  to  five  feet  to  a  mere  passage; 
at  the  outlet  or  mouth  against  the  valley  was  a  wide  expan- 
sion or  antechamber,  in  which  a  large  proportion  of  the 
greater  bones,  ox,  rhinoceros,  &c.  were  found.  This 
mouth  was  choked  with  stones,  bones,  and  earth,  so  that 
the  cave  was  discovered  by  opening  upon  its  side  in  a  stone 
quarry.  On  entering  the  cave,  the  roof  and  sides  were 
found  incrusted  with  stalactites,  and  a  general  sheet  of 
stalagmite,  rising  irregularly  into  bosses,  lay  beneath  the 
feet.  This  being  broken  through,  yellowish  mud  was 
found  about  a  foot  in  thickness,  fine  and  loamy  toward  the 
opening,  coarser  and  more  sandy  in  the  interior.  In  this 
loam  chiefly,  at  all  depths,  from  the  surface  down  to  the 
rock,  in  the  midst  of  the  stalagmitic  upper  crust,  and,  as 
Dr.  Buckland  expresses  it,  '  sticking  through  it  like  the 
legs  of  pigeons  through  a  pie-crust,'  lay  multitudes  of  bones 
of  the  following  animals; — 

CARNIVORA — hyaena,  tiger,  bear,  wolf,  fox,  weasel. 
PACHYDERMATA — elephant,  rhinoceros,  hippopotamus,  horse. 
RUMINANTIA — ox,  three  species  of  stag. 
RoDEimA — hare,  rabbit,  water-rat,  mouse. 
BIRDS — raven,  pigeon,  lark,  duck,  snipe. 


725.  Describe  Kirkrfale  Cave 

726.  What  animals  are  found  in  thin  cave  t 

18* 


210  GEOLOGY. 

The  hyaena's  bones  and  teeth  were  very  numerous — pro- 
bably two  or  three  hundred  individuals  had  left  their  bodies 
in  this  cave;  remains  of  the  ox  were  very  abundant;  the 
elephants'  teeth  were  mostly  of  very  young  animals  ;  teeth 
of  hippopotamus  and  rhinoceros  were  scarce;  those  of 
water-rats  very  abundant.  The  bones  were  almost  all 
broken  by  simple  fracture,  but  in  such  a  manner  as  to 
indicate  the  action  of  hyaenas'  teeth,  and  to  resemble  the 
appearance  of  recent  bones  broken  and  gnawed  by  the  liv- 
ing Cape  hyaena.  They  were  distributed  '  as  in  a  dog-ken- 
nel,' having  clearly  been  much  distuibed,  so  that  elephants, 
oxen,  deer,  water-rats,  &c.  were  indiscriminately  mixed  ; 
and  large  bones  were  found  in  the  narrowest  parts  of  the 
cavern.  The  peculiar  excrement  (album  graecum)  of 
hyaenas  was  not  rare;  the  teeth  of  hyaenas  were  found  in 
the  jaws  of  every  age,  from  the  milk-tooth  of  the  young 
animal  to  the  old  grinders  worn  to  the  stump :  some  of  the 
bones  were  polished  in  a  peculiar  manner,  as  if  by  the 
trampling  of  animals." 

26*2.  The  conclusions  to  be  drawn  respecting  these  ossifcr- 
ous  caverns  are — 1.  that  some  of  them  formed  the  dens  of 
ravenous  animals,  like  the  wolf  and  hyaena,  which  dragged 
in  the  carcases  of  other  animals,  and  feasted  upon  them  in 
quiet,  leaving  the  bones  to  be  covered  in  process  of  time  by 
incrustations  of  calcareous  matter;  2.  that  others  were  par- 
tially filled  by  these  means,  and  partly  by  the  drifting  in  of 
bones  and  dead  animals  by  some  extraordinary  inundation; 
3.  that  many  (fissures  especially)  were  filled  by  the  same 
drifting  process,  or  by  the  accidental  fulling  in  of  the  ani- 
mals; 4.  that  several  appear  to  have  been  used  during  suc- 
cessive ages  as  retreats  for  animals  of  all  kinds,  and  even 
for  man  himself,  as  remains  of  savage  life  are  found  in 
caverns,  the  floors  of  which  are  formed  of  calcareous  incrus- 
tations, mud,  and  the  bones  of  animals  extinct  long  before 
man  made  his  appearance. 


727.  What  is  remarkable  in  these  bones  ? 

728.  What  conclusions  are  drawn  concerning  these  ossiferous  caverns! 


RAISED   BEACHES StBMAKINE   FORF.STS.  211 


EXPLANATORY    NOTE. 

BOULDERS,  on  BOWLDERS — a  term  generally  applied  to  rounded 
masses  of  stone  lying  on  the  surface,  or  loosely  imbedded  in  the  sub- 
soil. Boulders  are  found  of  all  sizes,  those  of  granite,  syenite,  and 
primitive  greenstone  being  the  largest,  and  often  weighing  from  ten  to 
thirty  tons. 

DILUVIUM. — The  terms  diluvium,  alluvium,  and  collnvium,  are  to  be 
found  in  all  geological  works,  but  the  distinctions  made  between  them 
are  often  not  very  obvious.  Colluvium  (Lat.,  con,  together,  and  /wo,  I 
wash)  is  meant  to  apply  to  masses  of  detrital  matter  washed  together, 
without  hinting  at  the  nature  of  the  force  by  which  they  were  accu- 
mulated. Alluvium  (Lat.,  ad,  to)  is  generally  applied  to  matter  brought 
together  by  the  ordinary  operations  of  water,  such  as  river-silt;  while 
diluvium  (Lat.,  dis,  asunder),  on  the  other  hand,  is  regarded  as  implying 
the  extraordinary  action  of  water.  In  this  sense  diluvium  was  at  one 
time  restricted  to  those  accumulations  of  gravel,  &c.  supposed  to  have 
been  the  consequence  of  the  Deluge;  but  it  has  now  a  wider  significa- 
tion in  geology,  being  applied  to  all  masses  apparently  the  result  of 
powerful  aqueous  agency. 

MORAINES — the  name  given  in  Switzerland  to  the  longitudinal  depo- 
sits of  stony  detritus  which  are  found  at  the  bases  and  along  the  edges 
of  all  the  great  glaciers.  The  formation  of  these  accumulations  is  thus 
explained  by  Professor  Agassiz : — The  glaciers,  it  is  well  known,  are 
continually  moving  downwards,  in  consequence,  probably,  of  the  in- 
troduction of  water  into  their  fissures,  which,  in  freezing,  expands  the 
mass  ;  and  the  ice  being  thus  loosened  or  detached  from  the  rocks  be- 
low, is  gradually  pressed  forward  by  its  own  weight.  In  consequence 
of  this  motion,  the  gravel  and  fragments  of  rocks  which  fall  upon  the 
glaciers  from  the  sides  of  the  adjacent  mountains  are  accumulated  in 
longitudinal  ridges,  or  moraines.  . 

OSSEOUS  BRECCIA. — Any  rock  composed  of  an  agglutination  of  angu- 
lar fragments  is  designated  by  the  Italian  word  breccia ;  and  when 
fractured  bones  are  abundantly  mingled  with  the  mass,  it  is  termed  an 
osseous  breccia.  A  breccia,  or  brecciated  rock,  differs  from  conglome- 
rate or  puddingstone,  in  .having  its  component  pebbles  angular  and 
fragmented,  whereas  those  of  the  latter  are  rounded  and  water-worn. 

SUPERFICIAL  ACCUMULATIONS— CONTINUED. 
RAISED    BEACHES SUBMARINE    FORESTS. 

263.  Where  the  sea  and  land  join,  the  former,  by  the 
action  of  its  waves  and  currents,  soon  forms  a  level  beach 
or  shore,  along  which  is  strewn  sand,  gravel,  shells,  and 
other  marine  exuviae.  In  tidal  seas,  this  beach  is  succes- 
sively inundated  and  exposed  by  the  flowing  and  ebbing 

729.  Explain  the  terms  o^the  note. 

730.  What  of  raised  beaches  » 


of  the  waters ;  and  in  seas  where  there  is  no  perceptible 
tide,  the  winds  and  waves  gradually  form  a  fringe  of  drifted 
matter,  so  that  in  either  case  there  is  impressed  upon  the 
land  a  water-mark  which  it  is  impossible  to  mistake  for  any 
other  appearance.  Where  an  elevation  of  the  land  takes 
place,  th|s  beach  will  form  a  terrace  composed  of  sand,  gra- 
vel, and  other  marine  debris,  ranging  more  or  less  parallel 
with  the  new  line  of  coast:  such  terraces  are  known  by  the 
name  of  raised  or  ancient  beaches.  But  the  earth's  crust  is 
as  liable  to  depression  as  elevation  ;  and  though  depressions 
are  not  so  obvious,  in  consequence  of  the  overflow  of  the 
ocean,  still,  in  certain  localities,  the  ebbing  tide  exposes 
the  stumps  of  trees  and  other  terrestrial  evidences  of  these 
districts  having  at  one  time  formed  dry  land.  Phenomena, 
of  this  kind  are  known  as  submarine  forests,  and  are  classed 
with  ancient  beaches,  as  showing  the  depressing  and  ele- 
vating forces  to  which  the  terrestrial  crust  is  still  subjected. 
264.  Raised  beaches  have  been  discovered  in  many  parts 
of  the  world ;  in  some,  evinced  by  a  single  terrace,  in 
others,  by  a  succession  of  terraces.  Several  of  these  beaches 
are  comparatively  recent — as  the  Chili  upheave  of  1822, 
and  the  Ullah  Bund  at  the  mouth  of  the  Indus  in  1819  (par. 
74) — and  are  obviously  the  results  of  local  earthquakes  and 
volcanic  eruptions.  Others  are  of  more  ancient  date,  though 
still  coming  within  the  historic  period ;  while  most  of  the 
higher  terraces  evidently  belong  to  the  dawn  of  the  present 
geological  era.  Examples  of  such  phenomena  occur  in  the 
valleys  of  the  Forth  and  Clyde,  and  along  many  parts  of  the 
coast  of  Scotland.  One  terrace,  ranging  from  40  to  60 
feet  above  the  present  sea-level,  is  very  continuous,  and 
contains  the  shells  of  the  limpet,  whelk,  cockle,  common 
buccirium,  and  other  existing  species.  It  forms  the  plateau 
on  which  many  of  our  modern  sea-ports  are  situated,  arid 
preserves  an  outline  generally  parallel  with  the  existing 
shore.  Traces  of  a  lower  terrace,  ranging  from  6  to  15 
feet  above  the  present  high-water  mark,  occur  at  several 


731.  What  of  submarine  forests  1 

732.  What  oi'the  agency  of  volcanoes  and  earthquakes  ? 

733.  Describe  the  variety  of  these  beaches. 


RAISED  BEAPHES SI  BMARINE  FORESTS.  213 

points  on  the  eastern  coast;  but  doubts  are  entertained 
whether  it  might  not  be  the  result  of  other  causes  than  ter- 
restrial elevation.  As  in  Scotland,  so  in  England  evidences 
of  a  former  sea-beach  have  been  detected  along  the  coasts 
of  Lancashire,  Yorkshire,  and  Durham,  in  the  valley  of  the 
Mersey,  and  in  the  Bristol  Channel,  The  same  terraced 
appearances,  with  the  remains  of  existing  sea-shells,  are 
found  on  the  coasts  of  France,  Portugal,  Sicily,  Greece, 
Norway,  Sweden,  and  other  parts  of  the  European  sea-board. 
In  the  Mediterranean,  one  terrace,  nearly  50  feet  above 
the  sea,  and  full  of  shells,  is  discernible  at  many  distant 
parts  of  the  shore;  on  the  coast  of  Norway,  accumulations 
of  marine  shells  are  found  nearly  200  feet  above  the  exist- 
ing beach ;  and  along  the  borders  of  the  Baltic,  well-de- 
fined plateaus  of  marine  detritus  occur  at  elevations  varying 
from  50  to  100  feet.  All  these  examples,  with  many  others 
which  might  be  adduced  from  the  coasts  of  South  and 
North  America,  point  to  successive  elevations  of  the  land, 
analogous  to  those  by  which  the  stratified  formations  were 
raised  from  their  seas  of  deposit  into  open  day.  The  re- 
mains found  in  the  gravel  and  sand  of  these  beaches  are 
chiefly  shells  belonging  to  species  now  inhabiting  the  ocean, 
though  a  careful  examination  detects  varietits  apparently 
extinct.  The  more  elevated  terraces,  like  those  of  Scot- 
land and  Scandinavia,  are  evidently  of  great  antiquity,  and 
where  they  occupy  wide  expanses  in  ancient  firths  and 
bays,  are  apt  to  be  mistaken  by  the  superficial  observer  for 
true  diluvial  or  even  tertiary  gravels. 

265.  With  regard  to  the  origin  of  submarine  forests, 
geologists  are  somewhat  at  variance — one  clasl  of  theorists 
advancing  such  phenomena  as  evidences  of  submergence, 
another  contending  that  they  merely  occupy  low  flat  dis- 
tricts, which  have  been  successively  lost  and  won  by  the 
sea.  Without  advocating  either  hypothesis,  it  may  be  stated 
that  the  sites  of  these  so-called  forests  are  generally  flattish 
districts,  a  few  feet  under  the  ordinary  sea-level,  and  when 
exposed  after  a  storm,  or  during  ebb  tides,  present  a  series 


734.  What  is  tho  geological  reasoning  here  7 

735.  Name  the  theories  of  the  origin  of  these  forests  t 

10 


214  oroLOGr. 

of  half-fossilized  stamps,  with  their  roots  imbedded  in  a 
stratum  of  dark-blue  clay,  evidently  the  soil  in  which  they 
grew.  The  stumps  have  undergone  various  degrees  of  pe- 
trifaction, and  many  of  them  are  also  incrusted  with  iron 
pyrites.  Phenomena  of  this  kind  have  been  detected  in 
the  estuary  of  the  Tay,  in  the  Firth  of  Forth,  on  the  coast 
of  Hampshire,  and  other  places — proving,  to  all  appearance, 
that  the  land  in  which  they  grew  had  been  submerged  be- 
neath the  ocean.  Those  who  oppose  this  view,  suppose 
the  trees  to  have  grown  in  low  alluvial  tracts,  which  were 
sheltered  from  the  inroads  of  the  sea  by  sand-hills  and  other 
barriers,  and  that  on  these  barriers  being  broken  down,  the 
forests  were  overthrown,  and  their  trunks  and  roots  covered 
by  the  inundating  waters  of  the  ocean.  This  latter  hypo- 
thesis, however,  has  few  adherents,  the  submergence  of  land 
being  as  common  a  phenomena  as  its  elevation.  Submer- 
gences, like  those  of  the  Japanese  towns  in  1596,  of  Port 
Royal  in  1692,  of  parts  of  the  Portuguese  and  African  coasts 
during  the  Lisbon  earthquake  of  1775,  are  occurrences  to 
which  all  districts  have  been  and  are  still  liable;  and  there 
is  nothing  more  unusual  in  detecting  the  stumps  and  roots 
of  trees  on  the  bed  of  the  ocean,  than  in  perceiving  the 
houses  of  Port  Royal,  which  were  visible  for  nearly  a  cen- 
tury after  their  submergence. 

266.  The  conclusion  to  be  drawn  from  the  occurrence  of 
raised  beaches  and  submarine  forests  is,  that  the  crust  of  the 
earth  is  still  subjected  to  the  same  elevating  and  depressing 
forces  which  were  instrumental  in  modifying  its  surface 
during  the  deposition  of  the  earlier  formations.  The  results 
of  existing  forces  may  be  insignificant  when  compared  with 
those  of  former  periods,  but  they  are  precisely  analogous. 
An  elevation  of  100  feet  may  produce  a  very  narrow  terrace 
of  gravel,  where  the  land  shelves  rapidly  beneath  the  water; 
but  where  the  sea  is  shallow,  as  in  most  bays  and  estuaries, 
it  will  lay  bare  thousands  of  acres  composed  of  mud,  clay, 
sand,  gravel,  and  marine  exuviae.  A  new  formation  would 
thus  be  constituted  as  peculiar  and  as  characteristic  of  its 
era  arid  origin  as  the  tertitiary  or  any  other  system  of  strata. 

736.  What  conclusions  are  drawn  1 


MARINE  SILT,  SAND-DRIFT,  SHINGLE  BEACHES,  &C. 


MARINE  SILT,  SAND'DRIFT,  SHIN«LE  BEACHES,  &C. 

267.  Under  the  term  "  Marine  Silt"  is  comprehended 
all  those  masses  of  sand,  mud,  clay,  gravel,  &c.,  which  are 
still  in  progress  of  accumulation  along  the  existing  shores 
of  the  ocean.  Waves,  tides,  and  other  oceanic  currents, 
are  the  forces  by  which  they  are  collected  and  arranged, 
although  a  great,  perhaps  the  greater,  proportion  of  the 
material  is  derived  from  the  land  by  the  ceaseless  transport 
of  streams  and  rivers.  It  is  necessary,  however,  to  form 
geological  distinctions  between  marine,  estuary,  river  and 
lake  deposits,  as  far  as  practicable,  according  to  the  agency 
more  immediately  concerned  in  their  aggregation  ;  for  it 
is  only  by  so  doing  that  we  are  enabled  to  account  for  the 
peculiarity  of  their  organic  remains,  and  therefrom  to  form 
correct  ideas  respecting  the  character  of  the  earlier  for- 
mations. Along  the  entire  shore  of  the  ocean,  drifted 
matter  is  always  more  or  less  accumulating  ;  scantily  around 
headlands  and  exposed  places,  where  the  sweep  of  the  tidal 
current  is  powerful  ;  abundantly  in  .sheltered  bays  and  re- 
cesses. Of  the  extent  of  such  deposits  it  is  impossible  to 
form  any  thing  like  a  correct  estimate,  travellers  and 
voyagers  having  hitherto  directed  little  or  no  attention  to 
the  geological  features  of  the  t  nntries  which  they  visit. 
Instances  of  marine  silt  are  afforded  Sv  the  sands  of  Tents- 
moor  and  Pilmoor  between  the  Tay  and  St.  Andrews  in 
Scotland,  by  the  "  warp"  yearly  reclaimed  near  the  mouth 
of  the  Humber,  the  fens  of  Lincoln  and  adjoining  counties, 
the  extensive  sands  and  marshes  near  Yarmouth,  the  Chesil 
bank  at  Portland,  and  the  flats  of  Somerset  and  Gloucester 
on  the  estuary  of  the  Severn.  Some  of  these  tracts  are  of 
considerable  extent  ;  but  they  are  insignificant  compared 
with  what  has  taken  place  in  other  regions.  The  isthmus 
of  Sue/,  for  example,  uhich  is  now  27  miles  broad,  is  said 
to  have  doubled  its  width  since  the  time  of  Herodotus 
(4090  years  ago)  ;  Tehama,  a  country  on  the  Red  Sea,  has 
increased  from  three  to  six  miles  seaward  since  the  Chris- 


737.  Define  marine  silt. 

738.  What  instances  are -named  f 


216  GF.OLOGV. 

tian  era;  Tyre  and  Sidon,  sea  ports  mentioned  in  Scripture, 
are  now  several  miles  inland ;  hundreds  of  square  miles  of 
Holland,  and  the  other  Low  Countries  of  the  continent, 
are  the  direct  formation  of  the  existing  seas. 

268.  Sand~drift  is  so  intimately  connected  with  marine 
silt,  that  both  may,  without  much  impropriety,  be  con- 
sidered as  one  deposit.  When  the  latter  is  chiefly  com- 
posed of  sand  and  comminuted  shells,  its  surface,  on  being 
exposed  by  the  ebbing  tide,  becomes  so  dry  and  light  as  to 
be  easily  borne  about  by  the  wind.  Blown  into  slight  emi- 
nences and  irregular  ridges,  a  portion  of  it  is  placed  beyond 
the  reach  of  the  returning  tide,  and  this  process,  repeated 
year  after  year,  gives  rise  to  extensive  flats  of  sand  curiously 
blown  into  dunes  or  little  hillocks,  and  scooped  out  into 
hollows  or  bunkers.  The  seeds  of  the  arundo  arenaria 
(bent),  elymus,  and  other  maritime  plants,  soon  spring  up 
from  this  newly-acquired  land,  and  bind  it  together  by  their 
long  interweaving  roots ;  other  species  succeed ;  and  thus, 
in  process  of  time,  a  vegetable  sward  gathers  over  it,  and 
protects  it  from  farther  removal.  Such  accumulations  arc 
known  by  the  name  of  sand-drift,  and  are  of  all  ages,  from 
that  covered  by  many  inches  of  vegetable  soil,  and  brought 
under  the  plough  of  the  farmer,  to  the  loose  sand  which 
was  drifted  up  during  the  ebb  of  the  latest  tide.  Consider- 
able tracts  of  this  sandy  formation  are  to  be  found  skirting 
the  coasts  of  every  country — at  some  places  in  long  narrow 
fringes,  at  others  in  wide  expanses  of  many  thousands  of 
acres.  It  is  always  at  the  head  of  bays,  in  creeks,  and 
other  recesses,  sheltered  by  some  headland  from  the  sweep 
of  the  tidal  current,  that  such  deposits  occur ;  indeed,  by 
the  erection  of  artificial  jetties  or  projections,  fringes  of 
sand  may  be  collected  along  the  coast  of  any  tidal  sea. 
The  difficulty  of  preventing  tracts  of  this  nature  from 
shifting  and  drifting  about,  and  the  damage  which  follows 
to  cultivated  soil  by  sand  being  blown  over  it,  has  given 
rise  to  many  schemes  for  their  retention.  The  common 
bent  (arundo  arenaria)  is  regularly  planted  on  the  sandy 

739.  What  of  Tyre  and  Sidon  ? 

740.  Define  sand-drift,  and  its  dunes  and  bunkers. 

741.  How  is  drifting  prevented  ? 


MARINE  SILT,  SAND-OiUF  I,  SHINGLE  BEACHES,  &C.    217 

plains  of  Poland,  and  Lord  Palmerston  has  followed  the 
same  process  with  complete  success  on  a  large  tract  of 
sand-drift  between  Ballyshannon  and  Sligo  in  Ireland.  The 
French  government  plants  and  protects  forests  of  sea-pine, 
to  prevent  the  sands  of  the  Bay  of  Biscay  near  the  Garonnne 
from  being  drifted  inland ;  and  at  one  time  it  was  held 
penal  to  pull  the  bent  which  grew  upon  the  links  or  downs 
of  Scotland. 

269.  Shingle  beaches  are  those  accumulations  of  rounded 
and  water-worn  stones  which  are  piled  up  on  certain  parts 
of  the  coast  by  the  conjoint  action  of  the  waves  and  tides. 
They  occur  only  along  exposed  districts,  from  which  the 
sand  and  finer  debris  is  swept  onwards  to  the  more  shel- 
tered  recesses.     The  battering  force  of  the  waves  during 
high  storms  is  so  powerful,  that  masses  of  shingle  are  often 
found  from '4  to  12  feet  above  ordinary  tide-mark — leaving 
appearances  very  perplexing  to  the  geologist  who  is  unac- 
quainted with  the  force  of  waves,  the  weight  which  stones 
lose  when  immersed  in  water,  and  the  curious  wedge-like 
arrangement  which  takes  place  among  the  individual  peb- 
bles.    In  addition  to  the  forward  motion  imparted  to  these 
beaches  by  the  waves,  they  are  also  subjected  to  the  lateral 
current  of  the  tides;  arid  thus  riome  of  them  move  onward 
along  the  coast  with  so  perceptible  a  motion,  that  they  have 
been   designated    travelling  beaches.     Where   shingle    is 
found  at  considerable  altitudes,  or  in  places  now  removed 
from  the  sea,  it  is  apt  to  be  confounded  with  diluvial  matter ; 
but  an  attentive  examination  of  the  manner  in  which  it  is 
piled  up,  and  the  remains  which  it  contains,  will  prevent 
such  a  mistake. 

270.  The  fossils  imbedded  in  marine  silt,  sand-drift,  and 
shingle,  all  belong  to  existing  races,  though  some  of  these 
races  are  now  extinct  in  the  countries  where  their  remains 
are  found.    Marine  silt,  in  many  places,  must  be  as  ancient 
as  the  time  when  the  land   and  sea  received  their  present 
configuration  ;  and  from  the  peculiar  nature  of  its  formation, 
must  contain  both  land  and  marine  relics — the  latter,  how- 

742.  Define  shingle  beaches. 

743.  Define  travelling  beacheg. 

744.  What  of  the  fossils  here  1 


213  CROLCK3Y. 

ever,  greatly  prevailing.     Scarcel}   any  of  the  fossils 
petrified ;   most  of  them   retain  their  usual  structure  ;  and 
unless  where  the  sands   are  highly  calcareous  or  ferrugi- 
nous, there  is  no  such  thing  as  induration  among  the  ma- 
terials which  compose  these  deposits. 

SUBMARINE  DEPOSITS  AND   ACCUMULATIONS. 

271.  Submarine  deposits   are   those  which   take  place 
tinder  the  waters  of  the  ocean,  and  are  not  subjected  in 
any  measure  to  littoral  influences.    Of  such  deposits  geolo- 
gists know  scarcely  any  thing  with  certainty,  as  few  seas 
have  been  sounded  with  a  view  to  detect  the  nature  of  the 
material  accumulating  beneath.     This  only  we  know,  that 
where  soundings  have  taken  place,  mud,  sand,  shells,  bro- 
ken corals,  &c.,  have  been  found,  evidently  deposited  there 
by  submarine  currents,  which  are  modified  in  their  velocity 
according  to  the  inequalities  of  the  bottom.    Many  of  these 
currents    are    ascertained,    and    according    to  the  regions 
whence  they  come,  and  over  which  they  pass,  so  will  the 
material  be  which  they  are  depositing  along  the  bed  of  the 
ocean.     Thus  the  two  polar  currents,  as  they  direct  their 
course  to  the  equator,  carry  with  them  icebergs  and  floes 
laden  with  the   rocks  and  gravel  of  the  artic  and  antarctic 
islands ;  the  gulf  stream  transports  the  sea-weeds,  animal 
remains,  and  other  debris  of  equatorial  countries;  while 
the  outward  current  of  the  Mediterranean  deposits  in  the 
Atlantic  the  products  of  its  temperate  regions.     All  these 
agents  are  unceasingly  at  work ;  and  thus  strata  are  now  in 
formation  along  the  bottom  of  the  sea  which,  if  elevated 
into  dry  land,  would  vie  in  extent  with  many  of  the  second- 
ary systems* 

272.  Submarine  accumulations  have  been  detected  in  the 
Yellow    Sea,    which   is  rapidly    shoaling,  in  the  Gulf  of 
Mexico,   in  the  Caribbean  Sea,  the  German  Sea,  and  in 
other  divisions  of  the  great  ocean.     The  latter,  according 
to  Mr.  Stevenson,  is  deepest  on  the  Norwegian  side,  where 
the  soundings  give   190  fathoms;  but  the  mean  depth  of 

745.  What  of  submarine  deposits? 

746.  What  agencies  are  described  ? 

747.  What  of  submarine  accumulations  ? 


TER RACES  IN  VALLEYS.  219 

the  whole  basin  may  be  stated  at  no  more  than  31  fathoms. 
The  bed  of  this  sea  is  traversed  by  several  enormous  banks, 
one  of  which,  occupying  a  central  position,  trends  from  the 
Firth  of  Forth  in  a  north-easterly  direction  to  a  distance  of 
110  miles;  others  run  from  Denmark  and  Jutland  upwards 
of  105  miles  to  the  north-west ;  while  the  greatest  of  all — 
the  Dogger  bank — extends  for  upwards  of  354  miles  from 
north  to  south.  The  superficies  of  these  enormous  shoals 
is  equal  to  one-fifth  of  the  whole  area  of  the  German 
Ocean,  or  about  one-third  of  the  extent  of  England  and 
Scotland.  The  average  height  of  the  banks  measures 
about  78  feet,  the  upper  portion  of  them  consisting  of  fine 
and  coarse  siliceous  sand,  mixed  with  comminuted  corals 
and  shells.  As  in  the  German  Ocean,  so  in  all  other  seas 
agents  are  at  work  depositing,  however  slowly,  materials 
which  are  destined  to  form  part  of  the  stratified  formations 
of  future  continents  and  islands. 

TERRACES  IN   VALLEYS. 

273.  Terraces  on  the  sides  of  valleys,  like  those  along 
the  sea-coast,  indicate  levels  formerly  occupied  by  -water. 
The  latter  are  ancient  sea-beaches,  supposed  to  be  the  re- 
sult of  elevations  of  the  land;  the  former  may  arise  partly 
from  elevations  of  the  same  nature,  and  partly  from  their 
rivers  having  cut  for  themselves  a  deeper  channel.  Thus, 
a  terrace  in  an  estuary  or  river  opening  towards  the  sea 
may  be  considered  as  indicating  a  raised  beach  ;  but  ter- 
races inland,  and  above  the  level  of  this  beach,  undoubtedly 
owe  their  origin  either  to  the  drainage  of  lakes,  or  the 
deepening  of  river  channels.  River-terraces  are  in  gene- 
ral of  no  great  breadth,  but  sweep  along  the  sides  of  the 
valley,  looking  at  a  distance  like  a  road  embankment ; 
hence  the  term,  "  parallel  roads"  has  been  applied  to  those 
observed  in  Glen  Roy.  Their  surfaces  are  covered  to  a 
considerable  thickness-  with  sand  and  pebbles — showing 
the  long-continued  action  of  water  at  that  elevation.  In 
some  valleys  there  are  two  or  three  successive  terraces  (see 

748.  What  geological  reasoning  here  ? 

749.  How  aro  terraces  formed,  and  where? 

750.  What  varistv  of  teiraces  1 


t;::o!.oov. 


fig.),  marking  the  gradual  declension  of  the  rivers  to  their 
present  level ;  and  not  unfrequently  isolated  mounds  of 
gravel  (d)  stand  out  in  the  plain,  of  the  same  height  with 
some  of  the  terraces,  as  if  these  knolls  had  been  shoals  and 
sandbanks  when  the  water  occupied  a  higher  level. 


a,  Upper  terrace ;  6,  Lower  terrace  ;  c,  Existing  river  ;  d,  Isolated 
mound  of  gravel,  of  the  same  height  with  the  lower  terrace. 

274.  Such  terraces  are  found  indiscriminately  in  all 
parts  of  valleys — at  their  heads,  in  their  broad  expanses, 
and  in  their  estuaries.  They  are  frequent  where  rivers  de- 
scend from  mountainous  districts,  but  not  very  distinct  and 
definite  even  should  the  water  have  formed  glens  and 
valleys  of  erosion  many  hundred  feet  in  depth.  The  rea- 
son of  this  is,  that  the  sides  are  so  steep,  so  liable  to  land- 
slips and  other  waste,  that  the  terraces  gradually  become 
obliterated,  leaving  the  bank  as  one  continuous  inclination. 
On  the  sides  of  valleys,  properly  so  called,  the  case  is  other- 
wise, the  terraces  being  left  level  and  distinct  as  on  the 
day  they  were  deserted  by  the  waters.  These  appearances 
would  seem  to  indicate  the  existence  of  ancient  lakes  and 
other  accumulations  of  water  at  a  high  level,  which  were 
either  suddenly  or  gradually  drained  as  the  river  cut 
through  the  barriers  which  produced  them.  Indeed,  most 
of  the  valleys  in  our  own^island  appear  to  have  been  at  one 
time  mere  chains  of  lakes  and  morasses,  now  drained  in 
consequence  of  the  waters  which  flowed  from  them  having 
gradually  deepened  their  channels.  This  natural  process 
of  drainage  is  still  going  forward  amid  the  swamps  and 
lakes  of  other  countries ;  and  it  is  therefore  easy  to  con- 
ceive how  terraces,  beaches,  or  ancient  water-marks  are 
formed,  and  will  continue  to  be  formed,  until  rivers  have 

751.  Explain  the  diagram. 

752.  What  geological  reasoning  here  1 


DEPOSITS   IX    VALLEYS.  221 

worn  down  their  channels  to  the  lowest  depth  which  the 
relative  level  of  sea  and  land  will  permit.  Instances  occur 
in  Glen  Roy,  in  the  valleys  of  the  Tay,  Eden,  Tyne,  Wear, 
Tees,  Ouse,  and  other  British  rivers,  all  of  which  present 
the  same  level  shore-like  appearance.  Similar  terraces  or 
beaches  are  found  extending  along  large  tracts  in  the 
vicinity  of  the  great  American  lakes  — showing  that  these 
"  fresh-water  seas,"  as  they  are  not  inappropriately  termed, 
at  one  time  occupied  a  higher  level,  and  spread  over  much 
wider  areas. 

DEPOSITS    IN    VALLEYS. 

275.  Deposits  in  valley?,  as  distinguished  from  those  in 
lakes  and  estuaries,  are  of  a  very  complex  description.     In 
general,  they  consist  of  clay,  marsh-silt,  sand,  gravel,  and 
shingle — according  to  the  nature  of  the  country  through 
which  the  river  flows.     Rapid  streams  leave  along  their 
banks  only  the   heavier   stones  and  gravel,  and  carry  all 
light  and  impalpable  matter  to  their  embouchures.     Slug- 
gish rivers,  on  the  other  hand,  deposit  a  great  portion  of 
their  suspended    impuri  les  in  the  valleys  through  which 
they  flow,  thus  forming  inland  tracts  of  alluvial  soil.     All 
rivers,  however,  are  liable  to  sudden  freshets,  and  as  they 
wind  and  bend  their  way  seaward,  they  tear  up  formerly- 
deposited  matter — here  piling  up  masses  of  shingle  and 
boulders,  there  mounds  of  sand,  and  again  overlaying  the 
whole  with  a  covering  of  mud.     It  is  therefore  impossible 
to  say  what  was  accumulated  by  the  ordinary  and  what  by 
the  extraordinary  operations  of  rivers,  or  to  separate  the 
ancient   from    the   modern.     Again,   mrst  of  our  valleys 
(locally  termed  dales,  haughs,  carses,  &c.)  have  been  the 
sites  of  lakes  and  morasses  in  which  heterogeneous  silt  was 
deposited,  and  there  is  thus  an  insuperable  difficulty  in 
distinguishing  between  what  is  really  fluviatile  and  what 
lacrustine. 

276.  Without  making  too  nice  distinctions,  river  depo- 

753    What  of  the  lakes? 

754.  Define  and  describe  deposits  in  valleys. 

755.  What  geological  reasoning  is  here  T 

756.  What  of  river  and  lake  deposits  f 

10* 


222  GEOLOGY. 

sits  may  be  described  as  more  heterogeneous  in  theii 
material,  and  more  irregularly  laid  down,  than  those  of 
lacrustine  origin.  In  lakes,  the  gravel,  sand,  and  mud  are 
distributed  in  layers  according  to  their  respective  gravities, 
whereas  the  shingle,  gravel,  and  mud  collected  by  river- 
torrents  are  piled  up  without  respect  to  any  law  of  sedi- 
mentary arrangement.  Notwithstanding  this,  there  are 
valley-deposits  which  it  is  impossible  to  ascribe  either  to  the 
one  agency  or  to  the  other;  and  all  that  the  geologist  can 
do,  is  merely  to  describe  the  composition  and  the  nature  of 
the  organic  remains  which  may  be  imbedded  therein.  Of 
these  accumulations,  many  are  of  great  antiquity,  and  con- 
tain bones  of  the  mammoth,  elk,  deer,  horse,  ox,  bear,  wild 
boar,  wolf,  and  other  animals  now  extinct  in  the  regions 
where  their  relics  are  found ;  others  are  still  in  progress, 
connecting  the  present  with  the  past;  while  some  are  now 
far  removed  from  the  agencies  by  which  they  were  formed — 
the  rivers  having  shifted  their  channels  to  give  birth  to 
newer  formations. 

DELTAS    AND    ESTUARY    DEPOSITS. 

277.  Of  modern  deposits,  those  formed  in  estuaries  are 
the  most  perplexing  to  the  geologist,  on  account  of  the 
numerous  and  often  opposite  agencies  concerned  in  their 
production.  The  prevailing  agent  is  the  river  at  whose 
mouth  they  are  accumulated ;  and  this  brings  down  mud, 
sand,  gravel,  vegetable  debris,  and  the  remains  of  terrestrial 
animals — during  quiet  periods  the  most  impalpable  silt, 
during  inundations  the  most  heterogeneous  mixture.  Fur- 
.her,  the  deltas  of  rivers  subjected  to  periodical  inundations 
constitute,  during  the  dry  season,  low  flat  tracts  full  of 
swamps,  lagoons,  and  mud  islands,  which  nourish  the 
rankest  jungfe  growth,  gigantic  reptiles  and  amphibia,  beds 
of  shells,  and  shoals  of  fishes.  During  the  wet  season  many 
of  these  plants  and  animals  are  swept  seaward,  or  buried 
in  situ,  by  the  debris  brought  down  by  the  current.  Again, 
the  sea  acts  in  most  of  these  estuaries,  running  inland  from 

757.  What  of  deltas  and  estuary  deposits  ? 

7o>.   What  of  tlv>  variety  of  agencies  concerned  ? 


DELTAS  AND  ESTUARY    DEPOSITS.  223 

ten  to  a  hundred  miles,  and  consequently  depositing  marine 
detritus  and  marine  organisms  amid  those  of  a  terrestrial 
and  iresh-water  character.  The  student  cannot  therefore 
fail  to  perceive  how  very  complex  the  nature  of  such  depo- 
sits must  be,  and  how  necessary  it  is  to  exercise  caution  in 
pronouncing  what  agent  or  agents  were  concerned  in  the 
formation  of  any  individual  layer.  As  in  modern  estuaries, 
so  in  those  which  existed  in  former  times,  and  thus  the 
difficulty  arises  with  respect  to  the  alternation  of  marine 
a;id  fresh-water  strata  in  tertiary  basins,  the  mingling  of 
fresh-water  with  marine  organisms  in  the  wealden,  and  the 
complication  of  terrestrial,  fresh-water,  and  marine  products 
among  the  rocks  of  the  coal-measures.  Bearing  these  facts 
in  mind,  and  carefully  studying  the  formation  of  modern 
estuary  deposits,  the  geologist  is  prepared  to  account  for 
appearances  in  the  older  systems  of  strata,  which  would 
otherwise  remain  unsolved. 

278.  Estuary  deposits  may  be  said  to  consist  of  irregular 
layers  of  mud,  clay,  sand,  gravel,  and  vegetable  debris, 
intermingled  with  organisms  of  terrestrial;  fresh-water,  and 
marine  origin.  When  accumulated  to  such  an  extent  as 
to  constitute  dry  land,  they  form  rich  alluvial  tracts  of  a  level 
and  uniform  appearance,  decidedly  prejudicial  to  health, 
but  favourable  to  the  growth  of  the  cultivated  vegetables. 
In  inland  and  non-tidal  seas,  as  the  Mediterranean,  Gulf  of 
Venice,  and  Baltic,  the  agency  of  the  rivers  prevails,  form- 
ing deltas  and  shoals  which  gradually  encroach  upon  the 
limits  of  the  seas;  but  in  tidal  waters  oceanic  agencies  are 
also  at  work,  either  assisting  in  the  accumulation  of  estuary 
silt,  or  distributing  the  debris  brought  down  by  rivers  over 
areas  far  removed  from  their  embouchures.  The  accumu- 
lations of  this  kind  now  forming  are  almost  as  numerous  as 
the  streams  which  enter  the  sea;  but  the  notice  of  some  of 
the  more  extensive  is  all  that  the  limits  of  this  treatise  will 
allow.  And  here  the  student  should  bear  in  mind  one 
essential  difference  between  the  older  formations  and  those 
of  existing  estuaries ;  namely,  that  among  the  former  a 
great  uniformity  prevails,  not  only  in  mineral  composition, 

759.  Of  what  do  estuary  deposits  consist  ? 


2'24  «EOLOGT. 

but  in  the  kind  of  organic  remains  which  they  contain,  thus 
evincing  a  uniformity  of  climate  and  other  terrestrial  condi- 
tions; while  among  the  latter  scarcely  two  deposits  present 
one  feature  in  common.  The  Ganges,  for  example,  bears 
down  to  its  delta  the  spoils  of  the  tropics — palms,  canes, 
tree-ferns,  bones  of  elephants,  lions,  and  tigers;  the  Nile 
the  scanty  aquatic  plants  of  Egypt  and  bones  of  the  croco- 
dile, the  camel,  and  other  domestic  animals;  the  Niger  the 
hippopotamus,  rhinoceros,  and  camelopard  of  Central  Afri- 
ca ;  and  the  Mississippi  the  pines,  buffaloes,  elks,  and  deer 
of  North  America.  In  subsequent  ages,  should  these  de- 
posits be  elevated  into  dry  land,  nothing  could  be  more 
dissimilar  than  their  organic  remains,  and  yet  we  know  that 
they  belong  to  one  common  period  of  formation. 

279.  The  most  extensive  deposits  of  this  class  are  those 
of  the  Mississippi  and  Amazon  in  America,  the  Po  and 
Rhone  in  Europe,  the  Niger  and  Nile  in  Africa,  and  the 
Ganges  and  rivers  of  the  Yellow  Sea  in  Asia.  The  delta 
of  the  Mississippi  is  partly  of  oceanic  and  partly  of  fluviatile 
origin,  and  coilsists  of  alternations  of  blue  and  reddish 
clays  with  vast  rafts  of  buried  wood,  and  remains  of  the 
buffalo,  elk,  deer,  jaguar,  wolf,  fox,  and  other  animals  pecu- 
liar to  northern  regions.  [This  delta  at  the  mouth  of  the 
Mississippi  has  advanced  several  leagues  since  New  Orleans 
was  built.  Some  idea  may  hence  be  formed  of  the  force 
with  which  the  agency  of  rivers  acts  in  effecting  geological 
changes.]  The  plain  of  the  river  is  from  thirty  to  fifty 
miles  broad,  but  near  the  sea  it  widens  to  treble  that 
breadth.  The  whole  of  this  valley,  extending  for  hundreds 
of  miles  inland,  consists  of  recent  alluvium,  which  the  river 
is  perpetually  shifting  and  re-depositing.  The  most  cha- 
racteristic feature  in  the  deposit  is  the  rafts  of  drift-trees 
brought  down  every  spring,  and  which,  according  to 
Captain  Hall,  are  matted  together  into  a  net-work  many 
yards  in  thickness,  and  stretching  over  hundreds  of  square 
leagues.  Respecting  the  material  deposited  near  the  mouth 

760.  What  variety  is  indicated  ? 

761.  What  geological  illustrations  are  named  I 

762.  Where  are  they  most  extensive  ? 

763.  What  of  the  Mississippi  T 


DELTAS   AND   F.STLARV    DEPOSITS.  225 

of  the  Amazon,  we  have  less  particular  information ,  but  it 
is  stated  by  Captain  Sabine,  that  its  sediment  discolours 
the  waters  of  the  ocean  three  hundred  miles  .off  shore. 
This  sediment  is  constantly  carried  to  the  north-west  as  far 
as  the  mouth  of  the  Orinoco,  and  thus  an  immense  tract  of 
swamp  is  formed  along  the  coast  of  Guiana,  with  a  long 
range  of  muddy  shoals  bordering  the  marshes — the  whole 
being  gradually  converted  into  dry  land.  Although  on  a 
less  gigantic  scale,  the  deltoid  deposits  of  Europe  have,  even 
within  a  very  recent  period,  made  considerable  accessions 
to  the  land.  During  the  last  thousand  years,  that  of  the 
Rhone  has  gained  upon  the  Mediterranean  from  four  to 
six  miles.  "  Notre  Dame  des  Ports,"  says  Mr.  Lyell, 
"  was  a  harbour  in  898,  but  is  now  a  league  from  the 
shore;  Psalmodi  was  an  island  in  815,  and  is  now  two 
leagues  from  the  sea ;  and  the  Tower  of  Tignaux,  erected 
on  the  shore  so  late  as  1737,  is  already  a  French  mile 
from  it."  At  the  head  of  the  Adriatic,  the  Po  and  other 
streams  have  borne  down  so  much  sediment,  that  "  from  the 
northernmost  point  of  the  Gulf  of  Trieste  down  to  the  south 
of  Ravenna,  there  is  an  uninterrupted  series  of  recent  ac- 
cessions of  land  more  than  one  hundred  miles  in  length, 
which,  within  the  last  two  thousand  years,  have  increased 
from  ten  to  twenty  milts  in  breadth" 

280.  Turning  to  Africa:  lower  Egypt  is  the  gift  of  the 
Nile;  and  Herodotus  estimates  the  sediments  borne  down 
by  ihis  river  to  be  so  abundant,  that  if  diverted  into  the 
Red  Sea,  they  would  fill  it  up  in  ten  thousand  years.  The 
Nile  still  transports  its  annual  burden  of  debris,  but  the 
seaward  growth  of  the  delta  is  prevented  by  littoral  currents, 
which  sweep  it  onward  to  other  parts  of  the  Mediterranean. 
The  Niger  presents  one  of  the  best  examples  of  modern 
deltoid  deposits,  and  affords  the  geologist  much  insight  as 
to  the  manner  in  which  terrestrial,  fresh-water,  and  marine 
remains  become  imbedded  in  the  same  formation.  This 
delta,  as  yet  so  imperfectly  examined,  ranges  along  the 


764.  What  remarkable  instances  are  named  7 

765.  What.of  the  Nile  and  Lower  Egypt? 

766.  What  do  the  deltas  of  th«  Niger  show  t 


.    GEOLOGY. 

coast  for  more  than  two  hundred  miles,  having  a  beach  of 
sea-sand  slightly  elevated  above  its  general  level.  Behind 
this  beach,  stretching  inland  for  more  than  one  hundred 
and  fifty  miles,  there  extend  vast  expanses  of  swamp,  man- 
grove-jungle, and  mud  islands,  intersected  by  creeks,  la- 
goons, and  branches  of  the  river.  Over  this  expanse 
(annually  inundated  for  several  months)  deposits  of  sand, 
clay,  silt,  and  mud  are  constantly  taking  place,  burying 
within  them  the  remains  of  rhinoceroses,  hippopotami, 
crocodiles,  &c.  which  inhabit  the  jungle,  terrestrial  ani- 
mals which  the  current  transports  from  the  high  country, 
arid  myriads  of  shell-fish  arid  other  aquatic  races  which 
abound  in  the  lagoons.  Here,  then,  we  have  salt-water 
agencies  prevailing  for  many  leagues  inland  during  the  dry 
season;  gigantic  amphibia  at  all  seasons;  shell-beds  and 
formations  of  marl  in  the  lagoons;  terrestrial  animals  from 
inland;  jungles  and  morasses  to  form  lignite;  and  sand, 
mud,  and  gravel  to  form  sandstone  and  shale.  Should  a 
period,  therefore,  ever  arrive  when  the  delta  of  the  Niger 
shall  become  habitable  dry  land,  appearances  will  present 
themselves  perfectly  analogous  to  the  tertiary  formation, 
and  one  by  which  a  flood  of  light  is  thrown  upon  the  for- 
mation of  the  coal  measures. 

281.  The  delta  of  the  Ganges,  according  to  Major  Ren- 
nel,  is  considerably  more  than  double  that  of  the  Nile, 
occupying  not  less  than  an  area  of  44,000  square  miles. 
That  portion  of  it  which  borders  on  the  sea  is  composed  of 
a  labyrinth  of  rivers  and  creeks,  all  filled  with  salt-water, 
except  those  immediately  communicating  with  the  princi- 
pal branch  of  the  river.  This  tract  alone,  known  by  the 
name  of  the  Sunderbunds,  is  equal  to  the  whole  princi- 
pality of  VV'ales;  but  from  its  recent  alluvial  character,  is 
subject  to  numerous  shiftings,  though  ultimately  settling 
down  and  shoaling  up  the  Bay  of  Bengal.  The  quantity 
of  sand  and  mud  brought  down  by  the  Ganges  is  so  great, 
that  the  sea  only  recovers  its  transparency  at  the  distance 
of  sixty  miles  from  the  coast ;  thus  not  only  adding  new 


767.  What  agencies  are  named  ? 

768.  What  is  peculiar  in  the  deltas  of  the  Ganges  1 


DELTAS  AND  ESTUARY   DEPOSITS.  2*27 

material  to  the  shoals  and  islands  of  the  Sunderbunds,  but 
forming  immense  tracts  of  submarine  strata  at  various 
depths  from  four  to  seventy  fathoms.  As  Egypt  is  said  to 
be  "  the  gift  of  the  Nile,"  so  may  the  great  plain  of  China 
be  considered  as  the  gift  of  the  Hoang-Ho,  the  Kiang-Koo, 
and  their  tributaries.  The  same  agencies  which  formed 
the  habitable  plain  are  still  at  work,  gradually  shoaling  up 
the  Yellow  Sea,  and  converting  its  basin  into  solid  land. 
Navigators  speak  of  their  keels  ploughing  up  the  fine  im- 
palpable sediment  at  a  distance  of  six  and  eight  leagues  off 
shore,  along  which  a  perceptible  increase  is  taking  place 
every  year.  Sir  George  Staunton  infers,  from  certain  ex- 
periments, that  the  Hoang-Ho  contains  one  part  of  sediment 
in  every  two  hundred  ;  and  estimating  the  average  depth  of 
the  Yellow  Sea  to  be  one  hundred  and  twenty  feet,  calcu- 
lates that  this  river  by  itself  is  capable  of  converting  an 
English  square  mile  into  solid  land  in  the  course  of  seventy 
days. 

282.  From  the  examples  given,  the  student  will  perceive 
that  estuary  deposits — that  is,  deltas  or  deposits  taking  place 
at  the  mouths  of  rivers — are  among  the  most  important  in 
modifying  the  present  configuration  of  land  and  sea ;  that 
they  constitute  the  connecting  link  between  formations 
now  in  progress  and  those  of  distant  eras;  and  present 
appearances  which  enable  the  geologist  to  infer  as  to  the 
manner  in  which  the  greater  portion  of  the  stratified  sys- 
tems were  deposited.  Their  organic  remains  are  numerous; 
are  partially  fossilized,  or  differ  little  from  recent  wood, 
bones,  and  shells;  and  all  belong  to  vegetables  and  animals 
which  have  been  placed  upon  the  earth  since  the  com- 
mencement of  the  present  geological  era.  Where  tidal 
influences  prevail,  these  remains  are  chiefly  marine;  where 
river  inundations  predominate,  they  are  fresh-water  and 
terrestrial ;  while  others,  as  beds  of  oysters,  &c.  are  of  true 
estuary  origin. 


769.  What  of  the  Chinese  rivers,  and  the  reasoning  thereon 

770.  What  do  we  learn  by  these  examples  1 

771.  What  geological  facts  and  deductions  are  hereT 


228  GEOLOGY. 


LACUSTRINE,  OR  LAKE,  DEPOSITS. 

283.  By  lacustrine  deposits  are  meant  those  accumula- 
tions which  have  been  collected  in  fresh-water  lakes  since 
the   present  order   of  things    was   established.     Looking 
back  to  certain  coal-fields,  and  to  the  fresh-water  beds  of 
the  wealden  and  tertiary  strata,  we  have  almost  evidence 
sufficient  to  justify  the    conclusion,  that  these  beds  must 
have  been  formed  in  lakes,  or  at  least  in  estuaries  where 
quiet  fresh-water  influences  greatly  predominated.     Indeed 
it  is  impossible   to  conceive  of  a  condition  of  the  world 
without  inland    lakes,  morasses,    and   swamps,    in    which 
aquatic  races  flourished,  shell   rnarl  was  formed,  and  peat- 
moss accumulated.     But  the  boundaries  of  those  ancient 
lacustrine  deposits  are  now   obliterated ;  and  all  that  the 
geologist  can  do  is,  to  judge  of  the  manner  of  their  accu- 
mulation, and  the  nature  of  their  contents,  by  comparing 
them  with  similar  deposits  now  occupying  the  surface  of" 
the  earth,  or  still  in  progress  of  formation. 

284.  Modern    lake   deposits    consist  of  clay-silt,    sand, 
gravel,  rolled  pebbles,  beds  of  marl,  and  accumulations  of 
peat-moss.     Generally  situated  in    plains  or  hollows,  sur- 
rounded by  hills,  a  lake  receives  the  waters  and  debris  of 
several  streams,  and  its  quiet  expanse  performing  the  office 
of  a  great  settling  pool,  the  debris  falls  down  as  sediment, 
and  the  waters  pass  off  by  one  outlet  purged  of  all  their 
impurities.     This  sediment,  collecting  at  the  mouths  of  the 
streams,  forms  little   deltas,   which  gradually  push   them- 
selves forward  into  the  lake;  aquatic  plants  soon  spring  up 
on  their  surface,  whose  annual  growth  and  decay  constitute 
beds  of  peat ;  fresh-water  shell-fish  and  the  calcareous  de- 
bris of  the  springs  and  streams  collect  in  certain  localities 
as  marl ;  and  these  various  formations  repeated  and  con- 
tinued, in  process  of  time  shoal  up  the  lake,  which  forms 
a  flat  alluvial   tract,  swampy  at  first,  but  soon  acquiring 

772.  What  of  lacustrine  deposits  ? 

773.  Of  what  do  they  now  consist  ? 

774.  What  results  from  the  sediment  ? 


LACUSTRINE,  OR  L\KE,  DEPOSITS.  225 

firmness  and  dryness  for  the  purposes  of  cultivation.  Silted- 
up  lakes  are  rife  in  this  country  as  well  as  in  other  parts  of 
the  world ;  they  occupy  the  central  and  wider  parts  of  our 
dales  and  valleys ;  and  though  all  superficial  evidences  of 
the  lake  be  obliterated,  the  regular  manner  in  which  the 
materials  are  distributed  serve  readily  to  distinguish  lacus- 
trine from  fluviatile  silt.  Respecting  the  extent  of  surface 
occupied  by  lake  deposits,  it  is  impossible  as  yet  to  form  an 
accurate  estimate,  though  it  is  evident  that  the  soil  of 
most  inland  valleys,  both  in  this  and  in  other  countries,  is 
composed  of  it.  The  prairies  of  North  America,  the 
pampas  of  South  America,  and  the  steppes  of  Europe  and 
Asia,  are  regarded  by  many  as  the  sites  of  lakes  now 
drained  or  silted  up ;  and,  considering  their  relation  to  ex- 
isting rivers  and  valleys  of  drainage,  there  is  ample  foun- 
dation for  the  opinion.  Considerable  tracts  of  alluvial  land 
are  still  in  progress  of  formation  along  the  borders  of  most 
modern  lakes,  whose  sites  under  the  double  process  of  silt- 
ing up  and  drainage,  are  evidently  destined  to  become 
alluvial  plains  like  those  to  which  we  have  adverted.  By 
drainage  is  meant  that  tendency  which  rivers  issuing  from 
lakes  have  to  deepen  their  channels,  and  thereby  not  only 
to  lower  the  level  of  their  parent  waters,  but  also  to  render 
them,  from  their  shallowness,  more  liable  to  be  choked  up 
by  aquatic  vegetation. 

285.  Of  the  various  substances  composing  lake  deposits, 
marl  is  the  only  one  whose  formation  deserves  particular 
notice.  This  substance  may  be  looked  upon  as  the  lime- 
stone of  the  superficial  accumulations  just  as  the  chalk, 
oolite,  lias,  zechstein,  mountain  limestone,  and  cornstone, 
were  the  calcareous  beds  of  their  respective  formations.  It 
occurs  in  various  states  of  purity,  from  a  marly  clay,  which 
\vilJ  scarcely  effervesce  with  acids,  to  a  shell-marl  containing 
from  80  to  90  per  cent,  of  lime.  Marl-clay,  for  instance, 
occurs  as  a  whitish  friable  clay  with  an  admixture  of  lime, 


775.  How  are  silted  up  lakes  known  T 

776.  What  examples  of  such  alluvia  are  named  f 

777.  Define  drainage. 

778.  What  of  marl  and  its  varieties  I 


2-.0  GEOLOGY. 

and  sometimes  also  of  magriesian  earth ;  the  term  clay- 
marl  is  applied  when  the  calcareous  matter  prevails  over 
the  clay ;  shell-marl  is  almost  wholly  composed  of  lime 
and  fresh-water  shells,  with  a  trace  of  clay  or  other  earthy 
matter,  and,  where  solidified  by  chemical  aggregation,  is 
known  as  rock-marl.  With  respect  to  the  origin  of  these 
marls  there  are  various  opinions,  though  it  is  generally 
admitted  that  they  are  derived  partly  from  calcareous  springs 
which  enter  the  lakes,  and  partly  from  the  shells  and  secre- 
tions of  the  fresh-water  molluscs  which  inhabit  them.  What 
tends  to  confirm  this  opinion  is  the  fact,  that  marl-clay  and 
clay-marl  are  found  chiefly  among  the  deposits  of  ancient 
or  modern  lakes  situated  in  limestone  districts  where  cal- 
careous springs  abound;  and  that  shell-marl  is  often  almost 
wholly  composed  of  the  exuviae  of  molluscs,  many  genera 
of  which  are  still  inhabiting  the  same  lakes  and  marshes  in 
which  the  deposit  is  found.  Marl  occurs  irregularly  inter- 
stratified  with  clay-silt,  peat-rnoss,  or  gravel,  and  is  dug  for 
agricultural  purposes  in  many  of  the  ancient  lake-sites  and 
alluvial  valleys  of  Britain 

286.  The  organic  remains  found  in  lacustrine  deposits 
are  chieflly  fresh-water  shells,  such  as  limnaea,  planorbis, 
paludina,  cyclas,  mya,  cypris,  ancylus,  &c. ;  bones,  horns, 
and  other  portions  of  mammalia,  as  the  stag,  elk,  deer,  ox, 
horse,  bear,  fox,  beaver ;  detached  skeletons  of  birds ;  and 
drift  or  submerged  plants,  of  which  oaks,  pines,  birches, 
hazels,  reeds,  rushes,  and  other  vegetation  commonly  found 
in  peat-mosses,  are  the  most  abundant.  Human  skeletons 
are  occasionally  met  with  ;  and  canoes,  stone  battle-axes, 
&c.,  of  great  antiquity  have  been  dug  up  from  the  silt  of 
Loch  Doon  in  Ayr,  as  well  as  from  the  shell-marl  of  Kin- 
nordy  Loch  in  Forfarshire.  All  of  these  remains,  whether 
plants  or  animals,  belong  to  races  now  existing  upon  the 
globe,  although  some  genera  (as  the  elk,  wild-boar,  and 
beaver  in  Britain)  may  have  become  extinct  in  the  regions 
where  their  exuviae  are  found. 


779.  What  of  the  organic  remains  ? 


CHEMICAL  AND  MINERAL  DEPOSITS.  231 


EXPLANATORY  NOTE. 

EMBOUCHURE — a  term  adopted  from  the  French,  signifying  the  mouth 
of  a  river,  or  rather  that  area  over  which  its  current  spreads  as  it  enters 
auy  sea  or  lake. 

FRESHETS,  OR  LAND-FLOODS,  are  sudden  risings  of  rivers,  by  which 
they  inundate  their  banks,  and  carry  destruction  before  them.  The 
term  debacle  (from  the  French  debacler,  to  unbar)  is  often  used  instead ; 
but  more  properly  means  a  rush  of  water,  breaking  down  all  opposing 
barriers,  and  carrying  away  and  dispersing  fiagments  of  rocks  and 
other  debris. 

VALLEYS  OF  EROSION  are  those  which  have  been  formed  by  the 
abrading  power  of  water.  Rivers  having  a  rapid  descent  gradually 
deepen  their  channels;  year  after  year  their  banks  are  undermined, 
and  fall  into  the  current,  until  they  have  acquired  a  slope  sufficiently 
gentle  to  render  them  stable ;  but  this  stability  is  only  temporary,  for 
the  deepening  of  the  channel  goes  forward,  causing  the  bank  to  assume 
a  still  more  gentle  slope,  till  in  time  a  valley  of  considerable  width  is 
formed.  Such  are  termed  valleys  of  erosion,  in  contradistinction  to 
those  produced  by  the  silting  up  of  chains  of  lakes,  called  flat  valleys, 
to  those  caused  by  subterranean  sinkings,  called  valleys  of  depression, 
or  to  those  originally  formed  by  rents  and  fissures  resulting  from  earth- 
quakes. 

LAGOON  (Lat.,  lacuna,  a  morass) — a  term  originally  applied  to  those 
creeks  and  pools  which  abound  along  the  coast  of  the  upper  Adriatic ; 
but  now  employed  to  designate  all  similar  collections  of  water,  in 
whatever  region  they  occur.  Lagoons  are  sometimes  of  considerable 
depth  (those  enclosed  by  circular  coral  islands) ;  but  generally  they 
are  so  shallow  (those  of  deltas)  as  to  emit  noxious  exhalations. 

STEPPES — the  Russian  name  given  to  the  vast  system  of  plains  pecu- 
liar to  Northern  Asia.  It  is  synonymous  with  the  prairies  or  savannahs 
of  North  America  ;  and  the  pampas  or  ilhanos  of  South  America.  These 
plains  are  variously  classified,  according  to  the  level,  undulating,  or 
swampy  character  of  the  surface,  the  kind  of  vegetation  they  produce, 
and  other  obvious  appearances. 

SUPERFICIAL  ACCUMULATIONS— CONTINUED. 
CHEMICAL  AND  MINERAL  DEPOSITS. 

287.  Under  this  head  are  comprehended  all  those  superfi- 
cial accumulations  of  mineral,  saline,  or  bituminous  matter 
arising  from  the  action  of  springs,  evaporization,  subli- 
mation, or  other  natural  chemical  processes.  Such  pro- 
ducts are  extremely  numerous;  but  only  a  few  of  them 
exert  a  perceptible  influence  in  modifying  the  crust  of  the 
globe.  Calc-tujf  and  calc-sinter  are  deposited  by  calcareous 

780.  Define  and  explain  the  terms  of  the  Note. 

781.  Define  steppes,  and  give  its  synonymes. 

782.  What  and  where  are  chemical  and  mineral  deposits? 


UROLOGY. 

springs  after  the  manner  described  in  par.  53.  The  far- 
mer, as  the  name  tujfortufo,  implies,  is  a  porous  vesicular 
mass,  soft  when  first  deposited,  but  becoming  hard  on  ex- 
posure to  the  air,  so  as  to  resemble  marble  or  alabaster. 
It  is  generally  of  a  yellowish-white,  and  encloses  moss, 
twigs,  shells,  fragments  of  bones,  and  other  debris  that  may 
be  brought  within  reach  of  the  spring  by  which  it  is  de- 
posited. The  latter,  from  the  German  word  sintern,  to 
drop,  or  from  sinter,  a  scale,  is  more  compact  and  crystal- 
line, and  has  a  concretionary  structure,  owing  to  the  suc- 
cessive films  which  are  daily  added  to  the  mass.  Both  are 
found  around  the  sources  and  edges  of  calcareous  springs, 
sometimes  spreading  to  a  considerable  extent,  and  not  un- 
frequently  investing  high  cliffs  with  a  crust  of  unrivalled 
splendour.  Stalactite  and  stalagmite  are  kindred  produc- 
tions, both  being  produced  in  calcareous  caverns  by  the 
dropping  or  oozing  of  water.  The  former  (Gr.,  stalaktis, 
anything  which  drops)  are  those  pendents  of  carbonate  of 
lime  which  hang  from  the  roofs  of  caverns  like  icicles; 
they  are  formed  by  the  slow  dropping  of  calcareous  water. 
The  latter  (Gr.,  stalagma,  a  drop),  on  the  other  hand,  are 
the  crusts  and  protuberances  produced  on  the  floors  of  such 
caverns.  Sometimes  the  stalactites  and  stalagmites  meet, 
forming  pillars  and  arches  which  seem  to  support  the  roof. 
Caverns  adorned  in  this  manner  occur  in  Derbyshire,  in 
the  islands  of  Paros  and  Antipar  ;s,  and  in  other  parts  of 
the  world,  and  have  been  described  by  travellers  in  the 
most  fascinating  terms.  Tavertine  (a  corruption  of  the 
word  Tiburtinus)  is  another  calcareous  incrustation,  depo- 
sited by  water  holding  carbonate  of  lime  in  solution.  It  is 
abundantly  formed  by  the  river  Anio  at  Tibur,  near  Rome, 
at  San  Vignone  in  Tuscany,  and  in  other  parts  of  Italy. 
It  collects  with  great  rapidity,  and  becomes  sufficiently 
compact  in  a  few  years  to  form  an  excellent  building  stone. 
"  A  hard  stratum,"  says  Mr.  Lyell,  "  about  a  foot  in  thick- 
ness, is  obtained  from  the  waters  of  San  Filippo  in  four 
months;  and  as  the  springs  are  powerful,  and  almost  uni- 
form in  the  quantity  given  out,  we  are  at  no  loss  to  com- 

783.  Define  the  italicised  terms  of  this  page. 


CHEMICAL  AND  MINERAL  DEPOSITS.  233 

prehend  the  magnitude  of  the  mass  which  descends  the 
hill,  which  is  a  mile  and  a  quarter  in  length,  and  the  third 
of  a  mile  in  breadth,  in  some  places  attaining  a  thickness 
of  2-50  feet.  To  what  length  it  might  have  reached  it  is 
impossible  to  conjecture,  as  it  is  cut  off  by  a  stream  which 
carries  the  remainder  of  the  calcareous  matter  to  the  sea." 
Tavertine  is  a  light,  porous,  or  concretionary  rock,  well 
adapted  for  arches  and  other  structures  where  weight  is 
objectionable;  it  is  for  this  reason  that  it  has  been  used  in 
the  construction  of  the  cupola  of  St.  Peters. 

288.  Silicious  and  aluminous  deposits  derived  from 
springs  are  of  very  limited  extent — those  produced  by  the 
Iceland  geysers,  and  the  thermal  waters  of  the  Azores, 
being  the  only  examples  deserving  of  notice.  According 
to  Dr.  Webster,  the  hot  springs  of  the  Valle  das  Furnas,  in 
the  island  of  St.  Michael,  rises  through  volcanic  rocks, 
and  precipitates  considerable  quantities  of  silicious  sinter. 
Around  the  circular  basin  of  the  largest  spring  there  are 
seen  alternate  layers  of  coarse  sinter  mixed  with  clay,  in- 
cluding grasses,  fern,  reeds,  &c.,  in  different  states  of  petri- 
faction. Wherever  the  water  has  flowed,  sinter  is  found 
rising  eight  or  ten  inches  above  the  ordinary  level  of  the 
stream.  The  herbage  and  leaves  are  more  or  less  incrusted 
with  silex,  and  exhibit  all  the  successive  stages  of  petrifac- 
tion, from  the  soft  state  to  a  complete  conversion  into 
stone;  but  in  some  instances  alumina  is  the  mineralising 
material.  Fragments  of  wood,  and  one  entire  bed,  from 
three  to  five  feet  in  depth,  composed  of  reeds  common  to 
the  island,  have  become  wholly  silicified ;  and  a  breccia  is 
also  an  act  of  ibrmation,  composed  of  obsidian,  scori*,  and 
pumice,  cemented  by  silicious  sinter.  The  same  kind  of 
appearances  are  produced  by  the  geysers  of  Iceland  and 
several  other  thermal  waters.  Where  alumina  and  silica  are 
held  in  solution  by  the  same  spring,  the  deposit  produces  an 
admixture  called  lripoli,so  named  from  Tripoli  in  Barbary, 
where  a.  similar  compound  of  silica,  alumina,  and  oxide  of 
iron  is  abundantly  obtained  for  polishing  purposes.  All  the 

784.  What  of  silicious  and  aluminous  deposits  ? 

785.  Where  are  they  found  1 


234  GEOLOGY. 

varieties  of  tripoli  do  not  seem,  however,  to  be  derived  frotr. 
the  same  source  ;  -for  Ehreriberg  has  found  the  flinty  por- 
tion of  several  varieties  to  be  composed  of  the  silicioua 
coverings  of  animalcules.  The  fact  of  hot  springs  holding 
silica  in  solution,  its  converting  organic  matter  into  flint, 
and  forming  layers  of  tripoli  and  sinter,  is  of  high  import- 
ance to  the  geologist,  as  it  furnishes  him  with  data  to  reason 
respecting  the  origin  of  the  chalk-flints,  the  occurrence  of 
layers  and  nodules  of  chert  in  limestone,  and  other  appear- 
ances among  the  older  stratified  systems. 

289.  Bituminous  exudations — that  is,  springs  of  naphtha, 
petroleum,  &c. — are  very  abundant  in  some  countries, 
forming  pools  of  fluid  pitch  and  consolidated  masses  of 
asphalte,  and  impregnating  layers  of  sand,  clay,  &c.,  so  as 
to  render  them  inflammable.  Naphtha,  the  most  limpid  of 
the  bitumens,  is  found  exuding  from  the  earth  upon  the 
shores  of  the  Caspian  and  some  other  Eastern  countries. 
Near  the  village  of  Atniano,  in  the  state  of  Parma,  there 
exists  a  spring  which  yields  this  substance  in  sufficient 
quantity  to  illuminate  the  city  of  Genoa,  for  which  purpose 
it  is  employed.  It  is  generally  of  a  yellow  colour,  and  is 
readily  distinguished  Irom  other  bitumens  by  its  peculiar 
odour.  Springs  of  petroleum,  or  rock  oil,  are  found  in 
Modena,  Parma,  Sicily,  and  other  parts  of  Europe,  in  Syria 
and  Persia,  in  the  Burmari  empire,  in  Texas,  and  in  Bar- 
badoes,  whence  the  appellation  Barbadoes  tar.  It  is  a 
brown  thickish  liquid,  and  in  this  state  readily  mingles 
with  loose  rocky  substances,  so  as  to  render  their  mass 
bituminous.  On  exposure  to  the  air  it  becomes  viscous  or 
slaggy,  and  then  constitutes  mineral  pitch,  of  which  the 
lake  of  Trinidad,  and  that  of  Jefferson  county,  Texas,  are 
well-known  accumulations.  Asphalte  differs  from  mineral 
pitch  in  being  so  much  consolidated  as  to  be  rendered 
brittle.  It  is  found  on  the  surface  and  banks  of  the  Dead 
Sea,  in  Trinidad,  Barbadoes,  and  other  localities.  It  is 
supposed  that  these  products  are  sublimed  or  distilled  froin 


786.   What  of  bituminous  exudations  ? 

7S7.  Deline  naphtha  and  its  sources,  and  uses. 

78S.   What  of  petroleum,  asphalte,  &c.  ? 


CHEMICAL  AND  MlNfRAL  DEPOSITS.  £;£> 

bituminous  rocks  in  the  solid  crust  by  the  power  of  subter- 
ranean heat,  and  gradually  make  their  way  through  chinks 
and  fissures  to  the  suriace.  Whatever  be  the  source  from 
which  they  are  produced,  the  manner  in  which  they  mingle 
with  the  layers  now  forming  in  the  bottoms  of  lakes  and 
seas,  furnishes  the  geologist  with  analogies  which  may  aid 
him  in  accounting  tor  the  occurrence  of  bituminous  strata 
in  which  no  traces  of  vegetation  can  be  detected. 

290.  The  economical  uses  of  the  bitumens  are  too  well 
known  to  require  much  detail.     Asphalte  was  extensively 
used  by  the  ancients  as  a  cement ;  hence  the  name,  which 
is  derived  from  the  Greek,  a,  not,  and  sphallo,  I  slip — that 
is,  something  to  stick  together  with,  or  prevent  from  slip- 
ping.    It  is  now  used  extensively  in  the  manufacture  of 
materials  for  roofs,  linings  for  water-cisterns,  foot-pavements, 
&c.    Distilled  naphtha  is  extensively  employed  as  a  solvent 

.    for  caoutchouc,  and  is  also  occasionally  used  as  a  substitute 
for  oil  in  lamps. 

PEAT-MOSSES JUNGLE VEGETABLE  DRIFT. 

291.  Modern  vegetable  formations  are  commonly  distin- 
guished as  subterranean  forests,  peat-mosses,  jungle,  and 
vegetable  drift,  though  it  must  be  evident  that  in  many 
cases   no   real  distinction  can   be  drawn  between  them. 
Submarine  forests  have  been  already  noticed  (par.  265)  as 
evidences  of  terrestrial  submergence;  subterranean  forests 
are  those  accumulations  of  trunks,  branches,  and  roots 
which  occur  inland,  apparently  produced  by  the  inunda- 
tion and  subsequent  silting  up  of  low-lying  tracts,  in  which 
trees  flourished  abundantly.     But  as  the  subsequent  silt  is 
most  abundantly  composed  of  aquatic  and  other  peat-form- 
ing planis,  subterranean  forests  and  peat-mosses   may  be 
regarded  as  depending  upon  the  same  agency  for  their  pro- 
duction.    It  must  be  remembered,  however,  that  peat-bogs 
and  mosses  of  very  great  extent  are  to  be  found  in  northern 
countries  entirely  destitute  of  trees,  having  been  formed  by 

789.  How  is  it  produced,  and  to  what  uses  aplied  ? 

790    What  are  subterranean  forests,  and  how  produced  ? 

791.   Wh.it  of  peat-mosses,  j-mgles,  and  vegetable  drift  1 


236  GEOLOGY. 

the  annual  growth  and  decay  of  the  sphagnum  palustre  and 
other  marshy  vegetation.  With  respect  to  the  amount  of 
vegetable  matter  derived  from  tropical  jungles,  no  accurate 
information  has  yet  been  obtained,  though  analogy  would 
warrant  the  conclusion  that  the  result  is  too  important  to  be 
overlooked  by  geologists.  The  same  may  be  said  of  vege- 
table drift,  of  which  the  rafts  of  the  Mississippi,  already 
adverted  to,  afford  a  striking  example.  It  is  therefore  to 
subterranean  forests  and  peat-mosses  that  the  attention  of 
the  student  is  chiefly  directed,  these  being  by  far  the  most 
extensive  of  modern  vegetable  formations. 

292.  Subterranean  forests  are  found  in  estuaries  now 
silted  up,  in  ancient  lakes,  and  under  ordinary  peat-bogs. 
When  they  occur  in  estuaries  or  in  low  alluvial  lands  ad- 
joining the  sea,  they  would  seem  to  have  been  drilled  from 
inland  by  river  inundations;  for  most  of  the  trunks  and 
branches  lie  in  such  a  position  as  to  forbid  the  supposition 
that  they  grew  in  these  situations.  "  A  very  interesting 
case  of  this  kind,"  says  Professor  Phillips,  "  was  exhibited 
some  years  ago  by  the  deep  cutting  of  a  canal  connected 
with  the  Aire  and  Calder  navigation.  At  a  depth  of  twelve 
feet  from  the  surface  of  the  fine  alluvial  sediment,  here 
occupying  the  broad  valley  of  the  Aire,  a  quantity  of  hazel 
bushes,  roots,  and  nuts,  with  some  mosses,  fresh-water 
shells,  and  bones  of  the  stag,  were  met  with.  In  some 
parts  of  the  superjacent  sediments  an  English  coin  was 
found,  and  oars  of  a  boat  were  dug  up.  Where  a  little 
water  entered  this  peaty  and  shelly  deposit  from  the  adja- 
cent upper  magnesian  limestone,  it  produced  in  the  wood  a 
singular  petrifaction ;  for  the  external  bark  and  wood  were 
converted  into  carbonate  of  lime,  in  which  the  vegetable 
structure  was  perfectly  preserved.  In  like  manner  some 
of  the  nuts  were  altered;  the  shell  and  the  membranes 
lining  it  were  unchanged;  but  the  kernel  was  converted 
into  carbonate  of  lime,  not  crystallized,  but  retaining  the 
peculiar  texture  of  the  recent  fruit.  In  this  particular  case 
no  reasonable  doubt  can  exist  that  the  peaty  deposit,  full 

792.  What  example  is  related  ? 

793.  What  geological  inferences  are  drawn  f 


PEAT-MOSSES JUXULE VEOETARLE  DRIFT.  237 

of  land  mosses,  hazel  bushes,  and  fresh-water  shells,  was 
water-moved,  and  covered  up  by  fine  sediments  from  the 
river  and  the  tide."  As  with  the  example  now  quoted,  so 
with  numerous  accumulations  of  trunks,  roots,  and  branches 
of  trees  found  in  silted-up  estuaries  and  in  heads  of  bays 
both  along  our  own  coasts,  the  shores  of  the  Baltic,  and 
other  sea-boards.  Most  of  them  have  evidently  been  drifted 
thither  by  rivers  and  tidal  influences,  although  forests  in 
some  low  tracts  may  have  been  overthrown  and  buried  by 
inundations  of  the  sea.  When  subterranean  forests  occur 
beneath  lake  deposits,  or  under  ordinary  peat-bogs,  they 
point  to  causes  by  which  the  drainage  of  low  woody  valleys 
has  been  choked  up,  and  their  surfaces  covered  with  water, 
so  as  to  destroy  the  trees,  and  bury  them  by  subsequent 
accumulations  and  peat-growth. 

293.  Peat — or  turf,  as  it  is  often  called — is  a  natural 
accumulation  of  vegetable  matter,  varying  in  age  from  last 
year's  growth  to  that  which  was  formed  several  thousand 
years  ago,  and  in  appearance  from  a  loose  fibrous  mass  of  a 
brown  colour  to  a  dark  and  compact  substance  resembling 
lignite  or  brown  coal.  It  is  forming  in  all  marshes  by  the 
annual  decay  of  aquatic  vegetation,  and  is  encroaching 
upon  shallow  lakes  by  a  similar  process.  The  plants  which 
enter  most  abundantly  into  its  composition  are  the  sphag- 
num palustre,  or  "  peat-plant,"  a  number  of  mosses,  rushes, 
reeds,  and  other  marsh-loving  tribes,  crowned  in  some  situ- 
ations by  heather,  to  whose  antiseptic  properties  De  Luc 
ascribes  the  conservation  and  accumulation  of  the  other 
vegetable  substances.  Formations  of  peat  have  been  vari- 
ously classified  :  thus,  common  peat,  composed  of  the  stem, 
leaves,  and  roots  of  marsh  plants;  woody  peat,  derived  from 
the  branches,  leaves,  trunks,  and  roots  of  trees ;  peat-turf, 
the  heathy  turf  which  covers  moorland  districts ;  hill-peat, 
when  formed  on  the  sides  of  declivities;  and  peat-bog,  when 
it  accumulates  in  hollow  places,  or  on  flat  marshy  surfaces. 
Whatever  distinctions  may  be  made,  the  main  facts  con- 
nected with  their  formation  are  the  same — they  are  indi- 


794.  What  oftnrf  and  its  origin  7 
7P/V    What  varieties  of  peat  T 
]  1 


CEOLOOV. 


vidually  th,J  result  of  decomposed  vegetation  accumulate*! 
under  certain  conditions  and  in  particular  localities.  They 
are  to  be  met  with  in  almost  all  temperate  and  cold  moist 
countries,  whether  in  the  northern  or  southern  hemisphere. 
They  occur  abundantly  in  Scotland  and  England,  and  con- 
stitute a  large  proportion  of  the  surface  of  Ireland.  They 
occupy  vast  tracts  in  the  Netherlands,  Germany,  qnd  Russia, 
as  well  as  in  North  America  and  Canada,  and  are  to  be 
found  in  insular  regions,  as  Shetland,  Iceland,  and  the 
Falkland  Islands.  Oi  the  absolute  surface  occupied  by  peat, 
we  have  no  accurate  estimate;  but  some  idea  of  the  geo- 
logical importance  of  the  formation  may  be  formed  from  the 
fact,  that  one  of  the  mosses  on  the  Shannon  is  fifty  miles 
long,  and  from  two  to  three  in  breadth,  while  the  great 
marsh  of  Montoire,  near  the  mouth  of  the  Loire,  is  not  less 
than  fifty  leagues  in  circumference.  Some  of  the  Scottish 
mosses  have  been  dug  for  fuel  to  the  depth  of  twenty  feet, 
and  many  in  Ireland  are  reckoned  at  twice  that  thickness. 
It  must  be  borne  in  mind,  however,  that  nearly  one  half 
of  the  bulk  is  made  up  of  water,  and  that  the  mass  can  be 
reduced  by  compression  to  less  than  a  fifth  of  its  original 
thickness. 

294.  The  formation  of  peat,  as  has  been  stated,  is  con- 
fined to  moist  situations,  where  the  temperature  is  low,  and 
where  vegetables  may  decompose  without  putrefying.  It  is 
thus  found  in  swamps,  and  on  declivities  where  springs 
abound,  almost  entirely  composed  of  marsh  plants;  in  the 
sites  of  ancient  lakes,  covering  layers  of  gravel,  marl,  silt, 
&c.  and  mingled  with  earthy  impurities  ;  or  in  low  tracts 
whose  drainage  has  been  choke'd,  burying,  and  in  part 
formed  of,  the  trunks  and  branches  of  trees  which  flou- 
rished upon  those  spots  previous  to  their  inundation.  It 
increases  with  astonishing  rapidity,  instances  having  been 
known  where  fifteen  inches  in  thickness  had  been  formed 
in  twenty  years.  Being  light  and  spongy,  full  half  its  bulk 
is  composed  of  water,  and  tins  retentive  quality  enables 
new  races  of  plants  to  flourish  long  after  the  surface  of  the 

796.  What  peculiarities  in  relation  to  peat  ? 

797.  What  of  the  formation  of  peat  T 


PF.A  P-MOSSES — JUNGI.F. VEGETABLE  DRIFT. 

moss  has  been  raised  above  the  drainage-level  of  the  flat  in 
\vhich  it  occurs.  When  the  mass  has  sufficiently  accumu- 
lated to  change  its  character  from  that  of  a  shaking  morass 
to  a  firm  peal-bed,  the  marsh  plants  die  out,  and  are  suc- 
ceeded by  heatrfand  other  vegetation,  which  carry  on  the 
process  of  accumulation  at  a  less  rapid  but  still  perceptible 
rate.  Such  is  the  ordinary  mode  of  peat-growth,  concern- 
ing which  there  can  be  no  difference  of  opinion,  for  many 
of  the  accumulations  are  still  in  progress;  but  respecting 
those  collections  of  trees  which  are  often  found  buried  in 
the  mass,  geologists  are  far  from  being  agreed.  From  the 
varied  situations  in  which  such  collections  occur,  as  well 
as  from  the  different  positions  in  which  the  trunks  are  found 
in  the  mass,  it  is  evident  that  different  agencies  have  been 
at  work  in  their  aggregation.  In  river  valleys,  the  trees 
sometimes  appear  to  have  been  drifted,  and  subsequently 
silted  up  and  covered  by  peat-growth ;  in  general,  however, 
they  have  evidently  grown  where  they  occur,  and  been 
prostrated  either  by  natural  or  artificial  causes.  If,  for  ex- 
ample, the  drainage  of  a  wooded  valley  were  obstructed,  so 
as  to  render  the  soil  wet  and  "swampy,  the  further  growth 
of  the  forest  would  be  checked  ;  the  trees,  deprived  of  their 
firm  anchorage  in  the  ground,  would  be  easily  overturned 
by  winds;  and  as  they  were  pro.-; rn ted,  grasses,  reeds,  and 
marsh  plants  would  spring  up  through  their  branches,  and 
grow  rank  upon  the  nourishment  ai.'orded  by  their  decay. 
This  prostration  of  trunks  and  matting  of  vegetation  would 
further  obstruct  the  drainage  of  the  waters,  so  that  in  pro- 
cess of  time  the  whole  of  the  trees  would  be  overturned, 
and  the  valley  converted  into  a  swampy  morass.  In  such 
a  morass  peat  plants  would  luxuriate  till,  by  their  own 
growth  and  decay,  they  reached  a  height  beyond  that  of 
the  drainage-level,  when  their  accumulation  would  cease,  and 
a  peat-moss  be  completed  perfectly  analogous  to  many  of 
those  in  Ireland  and  Scotland.  The  same  result  would  fol- 
low whether  the  trees  were  prostrated  by  natural  or  artificial 
causes;  and  there  is  eyidence  afforded  by  the  trunks  in 
many  localities  thit  they  were  felled  by  man  at  no  very 


798.  What  geological  reasoning  is  here  1 


240  GEOLOGY. 

distant  era.  In  the  peat  of  Hatfield  Chace,  for  instance 
Roman  coins  and  axes  have  been  found,  some  of  the  latter 
still  fixed  in  the  wood :  a  rnedal  of  Gordian  was  found 
thirty  feet  deep  in  peat  at  Groningen  ;  and  De  Luc  has 
ascertained  that  the  very  site  of  the  aboriginal  forests  of 
Hercinia,  Senaar,  Ardennes,  &c.  are  now  occupied  by 
mosses-  and  fens — a  result  chiefly  brought  about  by  the 
Emperor  Severus,  who  ordered  all  the  wood  in  the  con- 
quered provinces  to  be  destroyed.  From  these  facts,  the 
student  will  perceive  how  necessary  it  is  to  examine  the 
mode  in  which  the  trunks  occur,  before  the  geologist  can 
venture  to  pronounce  as  to  their  collection.  If  the  trees 
are  cut  and  hewn,  man  must  have  been  concerned  in  their 
prostration  ;  if  they  are  merely  broken  over,  or  still  attached 
to  their  roots,  natural  causes  alone  have  been  at  work.  In 
general,  the  smaller  branches  have  decayed,  leaving  the 
trunk  and  larger  limbs,  with  fragments  of  the  bark  and  the 
root,  in  good  preservation.  The  trees  are  principally  oak, 
fir,  yew,  hazel,  birch,  ash,  and  willow  ;  they  lie  prostrated 
most  abundantly  towards  the  east  and  northeast ;  and  are 
often  of  very  gigantic  dimensions.  The  greater  number 
seem  to  have  undergone  considerable  decomposition  be- 
fore they  were  fully  enveloped  in  peat-growth  ;  shewing 
clearly  that  though  the  whole  iace  of  a  country  were  covered 
by  prostrated  forests,  it  would  only  be  in  marshes  and  peat- 
forming  hollows  that  the  trunks  could  be  preserved  from 
utter  decay. 

295.  Respecting  the  antiquity  of  peat-mosses,  we  can 
form  a  tolerably  correct  idea  from  the  nature  of  their  im- 
bedded fossils.  The  most  ancient  have  been  formed  since 
the  sea  and  land  received  their  present  configuration,  and 
since  the  latter  was  peopled  by  those  animals  which  now 
inhabit  it ;  for  from  none  have  we  well  authenticated  speci- 
mens of  greater  antiquity  than  the  existing  elk,  deer,  wild 
ox,  buffalo,  &c.  Indeed  the  greater  proportion  of  Euro- 
pean morasses  are  of  comparatively  recent  formation,  yield- 
ing the  canoes  and  skeletons  of  the  hair-clothed  aborigines 

799    Name  some  of  the  examples  cited. 
800.  What  of  their  antiquity  ? 


PEAT-MOSSES JtNGLK VKGT.  TABLE   DRIFT.  241 

—the  coins,  axes,  and  other  implements  of  their  Roman 
invaders — tlie  bones  and  horns  of  the  elk,  deer,  ox,  and 
other  animals  with  which  we  are  still  iamiliar.  Many  have 
even  been  formed,  as  it  were,  but  yesterday;  for  we  learn 
that  the  overthrow  of  a  forest  by  a  storm  about  the  middle 
of  the  seventeenth  century  gave  rise  to  a  peat-moss  near 
Lochbroom  in  Ross-shire,  where,  in  less  than  half  a  cen- 
tury after  the  fall  of  the  trees,  the  inhabitants  dug  peat. 
Whatever  be  their  relative  antiquity,  they  are  all  possessed 
of  great  interest,  from  the  evidence  which  they  afford  of  the 
rapid  accumulation  of  vegetable  growth,  and  from  the  per- 
fect manner  in  which  their  tannin  or  antiseptic  principles 
have  preserved  the  remains  of  man  and  the  lower  animals. 
\Ve  cannot  look  upon  the  vast  collection  of  trees  which 
they  contain,  without  being  reminded  of  a  period  when 
Britain  was  clothed  with  gigantic  forests;  on  the  rude  stone 
hatchets,  canoes,  and  skeletons  of  men  clad  in  skins,  with- 
out reverting  to  the  condition  of  our  earlier  ancestors;  or 
on  the  coins,  arms,  and  other  implements  of  the  Romans, 
without  associating  therewith  the  means  by  which  a  rude 
and  barbarous  country  was  reclaimed  to  culture  and  civili- 
zation. 

2=)6.  The  economical  applications  of  peat  constitute  one 
of  its  most  important  features.  Cut  in  rectangular  pieces, 
and  dried  bv  the  heat  of  summer,  it  forms  in  many  districts 
the  principal  fuel,  not  only  for  domestic  use,  but  for  burn- 
ing lime,  heating  corn  and  malt  kilns,  distilling  alcohol, 
&,c.  To  facilitate  the  process  of  drying,  the  water  is  some- 
times pressed  out  of  the  square  pieces  by  a  compressing 
machine,  which  also  renders  the  material  more  compact 
and  durable  in  the  fire.  Peat  is  occasionally  charred  by 
a  smoihered  combustion,  which  makes  it  a  more  suitable 
substitute  toi  coal  or  coke  in  the  smelting  of  iron  and  simi- 
}-r  purposes.  Attempts  have  also  been  made  to  extract 
tannin  from  its  mass,  to  be  used  instead  of  oak  and  larch 
bark  in  the  preparation  of  leather.  Decomposed  peat  forms 

801.  What  geological  and  historical  inferences  here  7 

802.  What  of  its  economical  uses? 


GF.OLOOV. 


an  excellent   mnmire  for  certain  soils,  and  is  now  exten- 
sively employed  in  modern  agriculture. 

SHFLL-BEDS,  CORAL-REEFS,  &C. 

297.  Th,  animal  accumulations  of  the  present  day,  like 
those  of  former  era?,  are  chiefly  discernible  in  the  exuviae; 
of  shell-fish  and  coral  animalcules.     It  is  true  that  the  re- 
mains of  fishes,  insects,  birds,  and  mammalia,  are  constantly 
being  entombed  in  the  deposits  now  taking  place;   but,  in 
point  of  quantity,  these  are  too  insignificant  to  constitute 
an  independent  stratum.     Such  remains   must  not,  how- 
ever, be  overlooked,  as  their  presence  in  any  deposit  will 
indicate  to  future  geologists  the  condition  of  the  world 
under  which  the  animals  flourished,  just  as  the  fossils  of 
older  formations  are  the  characters  by  which  we  can  inter- 
pret the  conditions  of  the  past.     Besides  the  gradual  en- 
tombment of  organisms  which  takes  place  in  the  ordinary 
course  of  nature,  there  are  extraordinary  causes  by  which 
hundreds  and  thousands  of  living  beings  are  destroyed  and 
buried  in  common  ruin.    The  desolation  of  populous  cities 
by  earthquakes,  the  destruction  of  flocks  and  herds  by  simi- 
lar catastrophes  or  by  river  inundations,  the  death  of  shoals 
of  fishes  by  submarine  exhalations,  the  drowning  of  clouds 
of  locusts,  and  the  like,  will  present  curious  appearances  in 
the  accumulations  in  which  they  are  imbedded;   and  it  is 
necessary  thnt  the  student  should  bear  such  possibilities  in 
mind,  otherwise  he  might  be  unable  to  account  for  peculiar 
aggregations  of  fossils  in  older  strata. 

298.  Shell-buds  are  accumulations  of  dead   and   living 
shells  found  under  the  waters  or  along  the  shores  of  exist- 
ing seas  and  lakes.     Dead  or  drifted  shells  are  strewn  over 
certain  localities  in  considerable  quantities   by  tidal  and 
other  currents;  fresh-water  varieties  are  found  in  lakes  con- 
stituting beds  of  marl;  and  many  gregarious  species  cover 
large  tracts  of  the  bottom  of  the  ocean.     Dead  shells  are 


803.  What  are  the  chief  animal  accumulations  1 

804.  To  what  agencies  are  the  variety  of  fossils  ascribed  I 

805.  What  of  shell-beds,  living  and  dead  1 


SHELL-BKDS,  t'OKAL-HKKFS,  &,C.  243 

thus  mingled  indiscriminately — genera  inhabiting  widely 
different  localities,  and  of  the  most  opposite  character,  being 
found  in  the  same  mass.  A  veiy  different  arrangement  holds 
with  respect  io  living  shells,  particularly  with  those  of  a  gre- 
garious character; — as  the  muscle,  cockle,  and  oyster.  These 
live  in  beds  or  families,  and  seem  to  be  governed  in  their 
growth  and  accumulation  by  circumstances  of  depth,  nature 
of  the  bottom,  and  food,  just  as  terrestrial  animals  are  regu- 
lated by  climate  and  other  vital  conditions.  Thus,  cockles 
and  muscles  delight  in  the  muddy  bottoms  of  tidal  estuaries, 
where  the  latter  often  form  beds  of  two  or  three  feet  in 
thickness,  and  several  miles  in  extent;  while  the  oyster,  at 
no  great  depth  from  the  sea-shore,  covers  the  bottom  for 
many  leagues,  to  the  exclusion  of  all  other  genera.  Should 
such  estuaries  ever  be  silted  up — and  there  is  ample  evi- 
dence of  like  occurrences — these  shells  would  form  strata 
precisely  analogous  to  those  beds  of  shell-limestone  which 
are  found  among  the  inferior  coal  measures,  the  new  red 
sandstone,  and  other  rock  formations.  Such,  in  fact,  is  the 
case;  and  in  many  estuary  and  lacustrine  deposits  shell- 
b^ds  present  themselves  partially  converted  into  .marl  and 
limestone;  while  in  raised  beaches  they  invariably  consti- 
tute the  most  interesting  phenomena. 

299.  One  distinction  between  the,  position  of  ancient  and 
recent  shell-beds  requires,  however,  to  be  specially  adverted 
to.  It  has  been  ascertained  that  various  genera  of  mollusca 
live  at  different  depths,  constituting  zones  of  marine  life 
analagous  to  zones  of  vegetable  growth  on  the  side  of  a 
mountain.  By  this  distribution  certain  families  are  littoral, 
others  live  at  depths  varying  from  100  to  600  feet,  while 
few  or  any  are  found  in  1000  feet  water.  In  general  terms: 
testaceous  animals  are  regulated  in  their  distribution  by 
depth,  by  the  nature  of  the  sea-bottom,  and  by  the  influ- 
ence of  submarine  currents;  the  number  of  families  is 
greatest  in  shallow  waters,  gradually  decreases  as  we  de- 
scend, and  finally  sinks  to  zero  in  the  depths  of  the  ocean. 
Such  an  arrangement  corresponds  with  all  our  ideas  of 
vitality :  shell-fish  can  no  more  subsist  under  the  pressure 

806.   Whit  of  tho  variety  ,n  depths  ? 


244  <;".oi,"f,r 

of  extreme  depth,  ;:bse;ice  of  ,Lght  and  f>od,  than  plants 
can  flourish  in  the  thin  cold  atmosphere  of  highly  elevated 
regions.  On  examining  the  crust  of  the  earlh,  however, 
strata  wholly  and  partially  composed  of  shells  are  found 
covered  by  many  thousand  feet  of  rocks;  but  as  the  ani- 
mals by  which  the  shells  were  formed  could  not  have  ex- 
isted at  such  depths,  we  are  led  to  the  conclusion  that  these 
shelly  beds  were  formed  at  moderate  depths,  that  the  bottom 
of  the  sea  was  subsequently  depressed,  and  received  those 
sediments  of  which  the  overlying  strata  are  composed. 
Strata  destitute  of  organisms  do  not  therefore  prove  the 
non-existence  of  marine  life  at  the  time  of  their  formation  ; 
they  may  have  been  formed  at  depths  so  enormous  as  ex- 
cluded the  mingling  of  testaceous  remains  with  their  com- 
ponent materials. 

309.  Carol  reefs,  already  adverted  to  in  pars.  95  and  86, 
are  chiefly  the  production  of  the  coral  animalcule,  and 
evince,  by  their  magnitude  and  extent,  the  powers  of  or- 
ganic agency  in  modifying  the  form  and  structure  of  the 
earth's  crust  As  in  the  case  of  the  sphagnum  palustre 
and  other  marsh  plants,  whose  growth  and  decay  went  to 
the  formation  of  peat-moss,  so  among  corals  race  after  r;ice 
departs,  each  leaving  its  stony  skeleton  as  a  foundation  for 
the  operations  of  succeeding  races,  which  are  destined  to 
make  way  in  turn  for  still  newer  generations.  According 
to  Ehrenberg,  the  coral  zoophyte  miy  be  regarded  as  a 
mere  secreting  membrane,  having  the  power  of  separating 
calcareous  matter  from  the  waters  of  the  ocean,  wherewith 
to  fashion  for  itself  an  internal  solid  skeleton  of  carbonate 
of  lime.  Around  and  within  the  radiated  pores  of  this 
frame  work  the  animalcule  lives  and  propagates  its  kind, 
expanding  itself  in  the  most  brilliant  colours  during  its 
secreting  operations,  and  contracting  and  withdrawing  itself 
within  the  pores  when  alarmed  by  danger.  Although  often 
exhibiting  the  most  beautiful  hues — crimson,  blue,  and 
yellow — in  their  native  element,  the  soft  parts,  when  taken 

807.  What  geological  reasoning  upon  this  ? 

808.  What  of  coral  reefs  1 

809.  What  of  the  coral  zoophyte  ? 

810.  In  what  varieties  are  they  found  f 


SHELL-IHUM, 


from  he  sea,  become  nothing  m;>re  to  appearance  th;m  a 
brown  slime  spread  over  the  stony  framework.  These  zoo- 
phytes swarm  in  incredible  numbers,  and  are  of  many  genera 
aadsnb-genera — each  spe- 
cies building  for  itself  a 
structure  peculiarly  fash- 
ioned and  decorated.  Ac- 
cording to  their  forms  the 
various  genera  are  com-  a: 
inonly  determined,  and 
thus  we  have  such  terms  as 
tree,  fan,  brain,  star,  and 
organ-pipe  coral,  known  to 
the  learned  by  their  syno- 
nymes — caryophyllia,  me- 
andriua,  astrsea  (see  fig.), 
porites,  madrepora,  tubi-  Mass  of  Astraeaviridis;  a,  a,  expanded 

pora,  and  the  like.  As  with       PolyPe,s !  6>  *•  Hypes  withdrawn 
.'      ,  into  their  cells;  c,  c,  stony  mass 

shell-hsh,  so  with  coral  am-       uncovered  by  flesh, 
rrials  ;  they  do  not  inhabit 

extreme  depths,  but  generally  carry  on  their  operations  along 
the  shores  of  rocky  islands  and  on  the  tops  o!  submarine  ridges 
not  more  than  one  or  two  hundred  feet  under  water.  Indeed 
the  principal  reef  builders  are  rarely  found  beyond  the  depth 
of  f  >rty  or  sixty  feet,  though  solitary  branching  corals  have 
been  dredged  in  fifty  and  even  a  hundred-fathom  water. 
Generally  speaking,  it  would  appear  that  the  coral  polype 
has  not  the  power  of  commencing  its  structure  at  great 
depths,  but  attaches  itself  to  comparatively  shallow  points 
within  the  influence  of  those  conditions  favourable  to  its 
development. 

33 1.  C<rral  polypes  in  active  operation  are  thus  de- 
scribed by  Captain  Basil  Hnll : — "  When  the  tide  has  left 
the  rock  tor  some  time  dry,  it  appears  to  be  a  compact  mass, 
exceedingly  hard  and  rugged;  but  as  the  tide  rises,  and  the 
waves  begin  to  wash  over  it,  the  polypi  protrude  themselves 


811.   Describe  the  diagram. 
812    What  of  deep  and  shallow  water? 
813.  What  description  of  their  work  is  h«"-«  f 
11* 


246  GEOLOGY. 

from  holes  which  were  before  invisible.  These  animals  are 
of  a  great  variety  of  shapes  and  sizes,  and  in  such  pro- 
digious numbers,  that  in  a  short  time  the  whole  surface  of 
the  rock  appears  to  be  alive  and  in  motion.  The  most 
common  form  is  that  of  a  star,  with  arms  or  tentacula, 
which  are  moved  about  with  a  rapid  motion  in  all  direc- 
tions, probably  to  catch  food.  Others  are  so  sluggish  that 
they  may  be  mistaken  for  pieces  of  the  rock,  and  are  gene- 
rally of  a  dark  colour.  When  the  coral  is  broken  about 
high-water  mark,  it  is  solid  hard  stone;  but  if  any  part  of  it 
be  detached  at  a  spot  where  the  tide  reaches  every  day,  it  is 
found  to  be  full  of  polypi  of  different  lengths  and  colours  ; 
some  being  as  fine  as  a  thread,  of  a  bright  yellow,  and 
sometimes  of  a  blue  colour.  The  growth  of  coral  appears 
to  cease  when  the  worm  is  no  longer  exposed  to  the  wash- 
ing of  the  sea.  Thus,  a  reef  rises  in  the  form  of  a  cauli- 
flower till  the  top  has  gained  the  level  of  the  highest  tides, 
above  which  the  animalcules  have  no  power  to  advance, 
and  the  reef  of  course  no  longer  extends  upwards." 

302.  The  composition  and  construction  of  coral  reefs, 
though  effected  chiefly  by  lime-secreting  zoophytes,  are 
still  owing,  in  a  great  measure,  to  the  pro:;  iscuous  aggre- 
gation of  marine  debris.  As  produced  by  the  zoophyte, 
coral  is  almost  a  pure  carbonate  of  lime,  soft  and  porous 
at  first,  but  gradually  becoming  so  hard  and  compact  as  to 
he  used  in  the  South-Sea  islands  for  building.  During  its 
formation,  however,  it  encloses  shells,  fragments  of  drift- 
coral,  sea-weeds,  star-fishes,  sea-urchins,  drift-wood,  and  the 
like;  and  these  being  cemented  in  one  mass  by  the  growth 
of  new  coral,  as  well  as  by  the  infiltration  of  dissolved 
carbonate  of  lime,  the  rock  presents  a  brecciated  appear- 
ance extremely  analogous  to  some  older  lime-stones.  Where 
reefs  have  been  upheaved  by  subterranean  agency,  and  are 
now  found  on  the  sides  of  hills  partially  overlaid  by  vol- 
canic tufa,  the  coral-stone  has  a  sparry  semi-crystalline 
aspect,  thus  presenting  the  geologist  with  almost  every 
gradation  of  limestone,  from  the  soil  chalky  mass  of  yester- 
tiay's  secretion  to  the  compact  texture  of  primary  marble. 


814.  How  do  corals  vary  in  composition  ? 


SHELL-BED*,  CORAL-REEFS,  &.C.  247 

303.  The  formation  of  enrol  islands  is  effected  in  the 
following  manner: — The  polypes  having  attached  them- 
selves to  the  rocky  bottom — say  on  the  summit  of  some 
submarine  ridge — proceed  to  build  upward  and  around, 
till  the  reef  remains  almost  dry  at  low-water  level.  Here 
they  leave  off  building  in  an  upward  direction,  but  still 
proceed  seaward,  increasing  the  breadth  of  their  structure, 
and  gradually  bringing  these  additions  up  to  the  surface, 
A  continuous  mass  of  calcareous  matter  is  now  seen,  com- 
posed principally  of  coral,  but  also  abundantly  of  shells, 
fragments  of  Crustacea,  and  other  sea-drift.  As  the  waves 
break  upon  the  new  elevation,  fragments  are  detached  and 
thrown  up,  shells  and  coral  sand  are  washed  upon  the  reef, 
and  these  being  cemented  together  by  calcareous  matter, 
form  a  low  ridge  exposed  to  the  influences  of  sun,  winds, 
and  rains.  In  this  state  rents  and  fissures  take  place  in  the 
mass,  new  fragments  are  detached  by  the  waves,  and  piled 
still  higher:  a  perpetual  rubbing  and  grinding  of  the  frag- 
ments produces  calcareous  sand,  which  is  gradually  drifted 
upwards  and  inwards,  filling  inequalities,  and  forming  in 
sheltered  recesses  a  narrow  beach.  Upon  this  new  territory 
sea-birds  alight,  nestle,  and  leave  their  droppings ;  sea- 
weeds and  other  marine  drift  are  added  ;  a  scanty  soil  is 
formed ;  seeds  are  drifted  or  borne  by  birds  from  the  ad- 
jacent continents  ;  plants  spring  up,  and  in  course  of  years 
clothe  the  infant  island  with  vegetation.  By  this  time 
strayed  land-birds  have  made  it  their  home;  insects  and 
reptiles  are  carried  thither  upon  drifted  trees,  either  alive 
or  in  the  larva  or  egg  state ;  and  lastly,  man  appears,  and 
takes  possession  of  the  gradually  increasing  soil.  Such  a 
mode  of  formation  supposes  no  elevation  or  submergence 
of  sea-bottom  by  volcanic  action.  But  in  the  Pacific,  where 
coral  reefs  are  most  extensively  developed,  subterranean 
movements  are  frequent — elevating  in  some  regions,  and 
depressing  in  others.  Thus,  a  gradual  elevation  would 
cause  not  only  a  more  rapid  rise  of  reef,  but  would  force 


815    What  of  coral  islands? 

816.  Whit  of  the  agencies  employed  ? 

817.  What  of  subterranean  or  volcanic  forces? 


243 

the  polype  to  opeiate  continually  further  seaward,  so  that 
the  mass  would  assume  a  broad  and  stratiform  appearance. 
A  gradual  depression,  on  the  other  hand,  would  not  only 
lessen  the  supermarine  extent  of  the  reef,  but  would  com- 
pel the  animalcules  to  build  perpendicularly  upwards,  in- 
stead of  laterally,  as  in  the  case  of  elevation.  From  the 
peculiar  forms  which  coral  reefs  assume,  it  is  more  than 
probable  that  both  elevations  and  depressions  are  in  pro- 
gress over  the  bottom  of  the  Pacific ;  of  the  former,  at  least, 
there  is  ample  evidence  in  ancient  reefs  occurring  inland 
and  at  considerable  elevations  above  the  sea.  Thus,  on  the 
summit  of  the  highest  mountain  of  Tahiti,  an  island  com- 
posed almost  entirely  of  volcanic  rocks,  there  is  a  distinct 
stratum  of  fossil  coral  ;  and  in  the  Isle  of  France,  a  bed 
ten  feet  thick  occurs  between  two  lava  currents. 

304.  The  various  forms  which  coral  retfs  present  are 
classed  by  Mr.  Stutchbury  in  the  following  order: — I. 
Circular,  consisting  of  a  strip  or  belt  encircling  a  lagoon, 
wliioh  comrnmunicates  with  the  main  ocean  by  one  or  more 
channels ;  2.  Flat,  consisting  of  a  tabular,  oval,  or  irregu- 
larly round  mass,  not  intersected  by  channels  or  lagoons; 
3.  Long-narrow,  consisting  of  long  narrow  ridges  or  islands, 
with  cross  channels  at  irregular  intervals;  4.  Encircling 
high  land,  but  separated  from  it  by  a  deep  concentric  chan- 
nel with  several  openings  into  the  main  sea.  To  account 
for  these  peculiar  configurations,  which  are  very  persistent 
over  the  whole  of  the  Pacific,  various  hypotheses  have  been 
advanced,  all  more  or  less  involving  the  idea  of  subterra- 
nean movements,  to  which  that  region  is  known  to  be 
subjected.  First,  Circular  reefs  or  atolls  are  supposed  to 
be  founded  upon  submerged  volcanoes — the  edges  of  the 
crater  forming  a  basis  for  the  coral,  and  its  interior  depth 
the  lagoon.  The  coral  islands  of  the  dangerous  Archipe- 
lago are  all  of  this  kind,  and  consist  of  circular  belts  from 
400  yards  to  one  mile  across  the  ring,  which  always  en- 
close a  lagoon.  They  are  seldom  raised  more  than  four 
or  six  feet  above  the  water;  are  abrupt  towards  the  ocean, 


818.  What  variety  of  form  in  coral  reefs  t        ^ 

819.  How  are  these  accounted  for  7 


SHELL-BEDS,  roK  AL-UKEF>,  &C-  '249 

which  rapidly  deepens  to  mure  than  190  fathoms;  vary  from 
two  or  three  to  150  miles  across;  and  are  intersected  by 
deep  channels,  which  allow  a  free  communication  between 
the  ocean  and  the  lagoons.  The  bottoms  of  the  latter  are 
often  strewed  with  dead  shells  and  fragments  of  coral  ; 
sometimes  contain  smaller  reefs,  and  give  birth  to  numer- 
ous corallines,  sponges,  and  shell-beds.  The  subjoined 
engraving  represents  the  atoll  form,  with  its  enclosed 
lagoon : — 


Distant  view  of  a  coral  island,  with  its  enclosed  lagoon. 

Second,  Flat  or  tabular  reefs  are  founded  upon  some  ele- 
vated portion  of  the  sea-bottom  ;  they  have  no  lagoons  or 
channels,  but  form  solid  islands  of  coral,  which  in  pro- 
gress of  time  become  covered  with  sand,  soil,  and  other 
debris.  Reefs  of  this  kind  often  exhibit  lines  of  stratifica 
lion  in  their  mass,  owing  to  the  drifting  of  sand,  shells 
&-c.,  over  their  flat  surface  during  the  time  ol  formation. 
Third,  Long  narrow  reefs,  which  are  of  common  occur- 
rence, are  evidently  founded  upon  submarine  ridges,  inter- 
rupted by  irregularities" and  depressions — such  depressions 
causing  the  channels  or  gaps  by  which  they  are  intersected. 
Many  of  this  class  are  of  great  length:  Captain  Flinders 
describes  one  on  the  east  coast  of  New  Holland  not  less 
than  350  miles,  unbroken  by  any  channel.  Fourth,  Reefs 
encircling  high  land,  but  separated  from  it  by  a  narrow 

820.  Explain  the  diagram  1 

821.  Explain  the  formation  of  each  variety. 


250  GEOI.QPT. 

channel,  indicate  a  submergence  of  the  islands  which  they 
surround  At  their  commencement  they  must  have  been 
in  connexion  with  the  shore;  a  submergence,  however, 
would  remove  them  from  it,  inasmuch  as  the  waters  would 
cover  them,  and  find  a  new  shore  farther  inland.  In  their 
new  position,  the  zoophytes  would  build  upwards,  forming 
perpendicular  masses  separated  from  the  land  by  a  greater 
or  less  expanse  of  water,  according  to  the  amount  of  sub- 
mergence, and  the  abrupt  or  gentle  ascent  of  the  land. 
This  class  is  beautifully  illustrated  by  the  reefs  which 
encircle  the  islands  Raiatea  and  Tahaa : — 


Such  are  the  general  forms  in  which  coral  islands  appear  ; 
though  it  must  be  observed  that  points  of  attachment  are 
afforded  by  many  portions  of  sea-bottom  upon  which  reefs 
are  reared  after  fashions  the  most  grotesque  and  irregular. 
395.  The  extent  and  magnitude  of  coral  reefs  are  so 
great,  as  to  be  put  in  comparison  with  those  of  the  older 
calcareous  formations.  They  throng  the  Pacific  over  a 
space  comprehended  between  the  30th  degree  of  latitude 
on  each  side  the  equator ;  the  Arabian  and  Persian  Gulfs 
abound  in  the  same  formation  ;  so,  also,  the  Indian  Ocean 
between  Madagascar  and  the  Malabar  coast.  Captain 
Flinders  describes  the  great  reef  which  follows  the  line  of 
the  north-east  coast  of  New  Holland  as  more  than  1000 
miles  in  lengih,  in  course  of  which  there  is  one  continued 

822.  What  of  the  diagram  ? 

823.  Where  are  they,  and  wnat  of  their  extent  7 

824.  What  example  is  named  ? 


SOILS.  2.">1 

portion  exceeding  350  miles,  without  a  break  or  passnge 
through  it.  The  thickness  of  the  mass  is  variable — in 
some  instances  less  than  twenty  feet,  and  in  others  more 
than  a  hundred.  Estimating  the  average  at  thirty  or  forty 
feet,  and  taking  into  account  the  vast  length  to  which  coral 
ridires  extend,  they  constitute  an  amount  of  calcareous 
matter  equal  to  any  of  the  older  limestones,  the  carbo- 
niferous alone  excepted. 

306.  The  growth  of  coral  is  by  no  means  rapid;  for  ob- 
jects long  submerged  have  been  dredged  up  merely  covered 
with  a  thin  incrustation.    It  is  stated  in  Captain  Beechey's 
Expedition  to  the  Pacific,  that  no  positive  information  could 
he  obtained  of  any  channel  having  been  filled  up  by  coral 
within  a  given  period,  and  that  several  reefs  had  remained 
for  more  than  half  a  century  at  about  the  same  depth  from 
the  surface.     By  others,  it  has  been  estimated  that  the  in- 
crease of  a  reef  is  generally  from  four  to  six  inches  in  one 
hundred  years;  but  this  is  little  better  than  conjecture;  for 
although  the  growth  of  coral  by  itself  be  a  comparatively 
slow  process,  yet,  by  the  accumulation  of  shells,  broken 
coral,  and  other  drirt,  a  reef  may  augment  at  a  more  rapid 
rate.     Whatever  the  rate  of  growth,  the  process  of  augmen- 
tation is  incessant ;  and  thus,  in  the  course  of  centuries, 
have  the  reefs  and  islands  of  the  Pacific  risen  above  its 
waters.     The  student  must  not,  however,  confound  eleva- 
tion above  the  ocean  wilh  strict  increase  of  coralline  matter; 
because  there  is  every  reason  to  conclude  that  vast  areas  of 
the  Pacific  are  undergoing  a  gradual  upheave,  by  which 
submarine  reefs  and  ridges  are  continually  being  brought 
to  the  surface,  and  existing  islands  further  enlarged  and 
elevated. 

SOILS. 

307.  The  superficial  coating  of  the  earth  on  which  plants 
hare  grown  and  decayed  is  properly  denominated  "  soil."    It 
is  chiefly  composed  of  inorganic  substances — that  is,  of 
clay,  sand,  lime,  &c. — with  an  admixture  of  decomposed 

825.  What  of  the  growth  of  coral  ? 

R26.  To  what  other  agencies  is  increase  ascribed  T 

827.  What  of  soil  and  its  composition  T 


252  GKULOGY. 

vegetable  and  animal  matter.  There  is  scarcely  a  portion 
of  the  earth's  crust  entirely  destitute  of  this  covering,  unless 
it  be  the  snow-clad  peaks  of  the  loftiest  mountains,  the 
newly-deposited  debris  on  the  sea-shore,  or  the  shifting 
sands  of  the  desert.  However  slight  the  admixture  of  or- 
ganic matter  may  be,  its  presence  constitutes  soil,  beneath 
which  is  the  subsoil,  comparatively  or  altogether  without 
such  admixture,  and  therefore  justly  classed  as  clay,  sand, 
gravel,  lime,  or  mixed  earth,  as  the  case  may  be.  Soil 
subserves  most  important  purposes  in  the  economy  of  cre- 
ation ;  without  it  there  could  be  no  succession  of  vegeta- 
tion ;  without  a  succession  of  plants  terrestrial  animals  could 
have  no  subsistence. 

308.  The  formation  of  soil  is  of  easy  comprehension. 
Suppose  a  tract  variously  composed  of  clay,  sand,  lime,  and 
other  primitive  earths  to  be  elevated  above  the  waters,  its 
mass  would  soon  become  dry  and  compact,  and  being  alter- 
nately subjected  to  the  sun  and  showers  of  summer,  and  to 
the  frosts  of  winter,  its  superficies  would  be  rendered  loose 
and  friable.  Over  this  expanse  birds  would  fly  and  animals 
roam,  mingling  their  droppings  with  the  earth,  and  adding 
their  carcases  and  other  exuviae  ;  the  winds  would  carry  the 
seeds  of  plants  from  other  regions,  and  these  springing  up, 
would  clothe  patches  of  the  waste  with  a  scanty  vegetation. 
Mosses,  lichens,  and  other  lowly  forms  would  spread  over 
the  rocks  and  gravel,  the  arundo  areriaria,  elymus,  &c.  over 
the  sands,  the  sphagnum  and  other  aquatic  tribes  in  the 
marshes,  and  grasses  on  the  silts  and  richer  portions.  The 
annual  growth  and  decay  of  these  plants  would  soon  form 
a  covering  of  vegetable  mould,  enriched  by  the  droppings 
and  exuviaa  of  animals  which  fed  upon  them;  and  thus  in 
process  of  time  would  the  region  present  varieties  of  soil 
capable  of  supporting  the  highest  forms  of  vegetation.  We 
see  such  a  formation  every  day  taking  place  ar  und  us; 
naturally,  in  those  districts  unreclaimed  by  agriculture,  and 
artificially,  where  manures  are  added  to  promote  its  fer 


828.  How  is  soil  and  subsoil  distinguished  ? 

829.  Describe  the  sources  of  the  formation  of  soil. 

830.  What  of  natural  and  artificial  soil? 


son?. 


til  it  v.  Independent  of  its  utility  to  the  vegetable  and  ani- 
mal economies,  soil  is  of  great  geological  importance,  inas- 
much as  it  lessens  the  amount  of  degradation  to  which  the 
crust  is  exposed.  Without  the  conservative  influence  of 
the  turf  which  protects  the  subsoils,  every  shower  and 
stream  would  wash  away  vast  quantities  of  the  loose  ma- 
terial, whereas  the  lightest  sand  is  secure  from  abrasion 
beneath  the  thinnest  grassy  covering. 

309.  Though  the  character  and  variety  of  soils  is  more 
the  study  of  agriculture  than  of  geology,  it  may  be  useful 
for  the  student  to  know  the  distinctions  which  have  been 
made  by  recent  writers  on  the  subject.  The  inorganic 
portion  of  soils  consists  of  what  are  called  the  primitive 
earths — namely,  clay,  silex  or  sand,  lime,  and  magnesia — 
and  of  certain  saline  and  metallic  compounds,  such  as  com- 
mon salt,  gypsum,  soda,  potash,  and  the  oxides  of  iron  and 
manganese.  The  organic  constituents  are  decomposed 
vegetable  and  animal  matters,  the  progressive  decomposi- 
tion of  which,  in  conjunction  with  inorganic  substances, 
air,  and  water,  furnish  chemical  compounds  of  humus,  car- 
bon, ammonia,  &c. — all  of  which  are  essential  to  the  per- 
fection of  vegetable  growth.  Sand  and  clay  being  the 
bulky  components  of  soils,  a  soil  is  said  to  be  sandy  when 
it  contains  no  mote  than  10  per  cent,  cf  clay;  a  sandy 
loam  if  from  13  to  40  per  cent,  of  clay;  and  loam  if  from 
40  to  70  per  cent.  On  the  other  hand,  should  the  clay 
average  from  70  to  85  per  cent ,  it  is  denominated  a  clay 
loam;  from  85  to  95,  a  strong  clay;  and  if  no  sand  be  pre- 
sent, it  is  pure  agricultural  clay.  The  same  sort  of  dis- 
tinctions are  made  when  lime  is  present  in  considerable 
abundance — 5  per  cent,  of  carbonate  of  lime  constituting  a 
marl,  and  20  per  cent,  a  calcareous  soil.  Where  soils  are 
immediately  derived  from  the  rocks  beneath,  they  partake 
of  the  same  chemical  character ;  and  where  separated  by 
layers  of  sand,  clay,  and  gravel,  they  are  still  influenced  in 
their  capacities  for  moisture  by  the  porous  or  open  texture 
of  the  subjacent  strata.  There  is  thus  an  intimate  con- 

831.  What  of  inorganic  and  organic  portions! 

832.  What  of  varieties  in  soil  1 


254  GEOLOGY. 

nexion  between  the  deductions  of  geology  and  agriculture 
— a  connexion  which  will  be  more  fully  pointed  out  in  a 
subsequent  section. 

EXPLANATORY  NOTE. 

ALABASTER — a  white  semi-transparent  variety  of  gypsum,  or  sul- 
phate of  lime.  It  is  a  mineral  of  common  occurrence,  and  is  manu- 
factured into  ornamental  vases,  and  occasionally  into  small  statues. 
The  ancients  used  it  for  ointment  and  perfume  boxes. 

MINERAL  NAPHTHA  is  generally  found  of  a  yellowish  colour,  but  may 
be  rendered,  colourless  by  distillation.  Its  specific  gravity  is  about 
three-fourths  that  of  water ;  it  boils  at  160  degrees ;  and  appears  to 
be  a  pure  hydro-carbon,  consisting  of  36  of  carbon  and  5  of  hydrogen. 
It  is  highly  inflammable,  and  burns  with  a  white  smoky  flame.  A 
liquid  very  similar  to  mineral  naphtha  is  obtained  by  the  distillation  of 
coal-tar. 

PROSTRATION  OF  TREES  — It  has  been  stated  that  the  trunks  found  in 
British  peat-mosses  are  most  abundantly  prostrated  towards  the  east 
and  nortli-east.  This  is  just  what  might  be  expected  where  the  trees 
have  bei  n  overthrown  by  natural  forces  ;  for  not  only  are  our  most 
prevalent  winds  from  the  west  and  south-west,  but  our  highest  and 
most  destructive  gales  are  also  from  the  same  quarters. 

CORAL. — Some  varieties  of  this  substance  have  long  been  in  request 
for  ornamental  purposes — their  value  depending  upon  the  size,  solidity, 
and  colour  of  the  specimen.  Black  and  red  varieties  are  the  most 
highly  prized,  portions  of  Sicilian  coral  having  been  known  to  bring 
so  much  as  eight  or  ten  guineas  per  ounce.  The  price,  however,  is 
extremely  variable,  other  portions  of  the  same  mass  selling  for  less 
than  a  shilling  a  pound.  Regular  coral  fisheries  are  established  in  the 
Straits  of  Messina,  on  the  shores  of  Majorca  and  Minorca,  the  coast  of 
Provence,  and  in  other  parts  of  the  Mediterranean.  Abundant  sup- 
plies are  also  obtained  from  the  Red  Sea,'  the  Persian  Gulf,  the  coast 
of  Sumatra,  &c. 

SUPERFICIAL    ACCUMULATIONS— CONTINUED. 
EARTHQUAKES    AND    VOLCANOES. 

310.  The  effects  produced  by  earthquakes,  in  as  far  as 
elevations  and  depressions  of  the  earth's  crust  are  concerned, 
have  been  already  alluded  to,  but  the  various  results  by 
which  they  are  followed  require  further  attention.  An 
earthquake  may  produce  a  momentary  undulation  of  the 
ground,  followed  by  no  perceptible  result ;  it  may  simply 
elevate  one  region  or  depress  another;  it  may  be  attended 
by  a  vast  destruction  of  animal  life,  and  the  submergence 

833.  Define  and  explain  the  terms  of  the  note. 

834.  What  various  effects  are  ascribed  to  earthquakes  ? 


FARTITQrAKFS  AND   VOU  \\OF.S.  l2.>.> 

of  f<  rests;  it  may  alter  the  course  of  rivers,  and  produce 
new  shores  and  beaches;  it  may  create  vast  tidal  waves, 
which  give  rise  to  accumulations  of  debris;  open  new 
springs  and  fissures,  from  which  issue  various  products 
differing  from  those  hitherto  known  in  the  district.  In- 
nuir.erable  instances  of  such  changes  could  be  cited  ;  a 
feu,  however,  will  suffice  to  convince  the  student  of  the 
importance  of  this  class  of  geological  agencies: — By  the 
gre?.t  Chili  earthquake  of  1822,  an  immense  tract  of  ground 
— not  less  than  100,000  square  miles — was  permanently 
elevated  from  two  to  six  feet  above  its  former  level ;  and 
part  of  the  bottom  of  the  sea  remained  bare  and  dry  at  h.gh 
wH-er,  with  beds  of  oysters,  muscles,  and  other  shells  ad- 
hering to  the  rocks  on  which  they  grew,  the  fish  being  all 
de;  d,  and  exhaling  most  offensive  effluvia.  By  an  earth- 
quake in  1819,  a  tract — the  Ullah  Bund — in  the  delta  of 
the  Indus,  extending  nearly  fifty  miles  in  length  and  sixteen 
in  breadth,  was  upheaved  ten  feet;  while  adjoining  districts 
were  depressed,  and  the  features  of  the  delta  completely 
ai'ered.  So  also  with  the  valley  of  the  Mississippi  in  1811, 
which,  from  the  village  of  New  Madrid  to  the  mouth  of 
the  Ohio,  was  convulsed  to  such  a  degree  as  to  create  lakes 
and  islands.  The  earthquakes  of  Calabria,  which  lasted  for 
nearly  four  years — from  1783  to  the  end  of  1786 — produced 
numerous  fissures,  landslips,  shifts  or  faults  in  the  crust, 
new  lakes,  ravines,  currents  of  mud,  falls  of  the  sea-cliffs, 
and  other  changes,  which,  taken  in  conjunction,  afford  the 
geologist  one  of  the  finest  examples  of  the  complicated 
alterations  which  may  result  from  a  single  series  of  sub- 
terranean movements,  even  though  of  no  great  violence. 
In  1743  the  town  of  Guatimala,  in  Mexico,  with  all  its 
riches  and  eight  thousand  families,  was  swallowed  up,  and 
every  vestige  of  its  former  existence  obliterated ;  the  spot 
being  now  indicated  by  a  frightful  desert  four  leagues  dis- 
tant from  the  present  town.  In  1692  a  similar  calamity 
overtook  the  town  of  Port  Royal,  in  Jamaica,  when  the 
whole  island  was  frightfully  convulsed,  and  about  1000 
acres  in  the  vicinity  of  the  town  submerged  to  the  depth  of 


835.  What  examples  are  cited  1 


250 

fifty  feet,  burying  the  inhabitants,  their  houses,  and  the  ship- 
ping in  the  harbour.  Such  examples  might  be  multiplied 
indefinitely,  even  within  the  limits  of  the  historic  period; 
but  enough  has  been  quoted  to  show  the  extensive  nature 
of  the  changes  which  may  have  been  produced  upon  the 
superficies  of  the  globe  since  the  commencement  of  the 
current  era. 

311.  Volcanic  forces  act  in  a  similar  manner,  in  as  far  as 
they  elevate,  depress,  and  break  asunder  portions  of  the 
earth's  crust;  indeed  earthquakes  and  volcanic  throes,  con- 
sidered as  subterranean  movements  merely,  produce  pre- 
cisely the  same  results.  But  volcanoes,  properly  so  called, 
act  in  another  and  equally  important  manner  in  producing 
geological  changes.  They  elevate  the  crust  into  long  con- 
tinuous ridges  or  mountain  chains,  form  isolated  cones,  and 
discharge  accumulations  of  lava,  scoriae,  ashes,  loose  stones, 
and  other  igneous  debris.  The  same  effects  have  been 
produced  by  igneous  forces  in  all  ages,  as  are  amply  evi- 
denced by  the  granitic  rocks  of  the  primary,  and  by  the 
trapptan  eruptions  of  the  secondary  and  tertiary  epochs. 
Volcanic  rocks  represent  the  igneous  products  of  the  pre- 
sent era,  and  are  associated  with  the  superficial  accumula- 
tions, just  as  the  older  traps  are  with  the  coal  measures, 
oolite,  and  chalk  strata.  The  granitic  and  trap  locks  occur 
either  as  disrupting,  interstratified,  cr  overlying  masses; 
so  do  the  volcanic:  the  former  cover  extensive  districts,  and 
form  vast  mountain  ranges;  so  do  also  the  latter,  as  will  be 
seen  by  an  enumeration  of  some  of  the  more  celebrated 
volcanoes.  In  Europe  there  appears  to  be  three  centres  of 
volcanic  action — namely,  that  of  the  Levant,  to  which  ^Etna 
and  Vesuvius  belong;  that  of  Iceland,  represented  by  Hecla; 
and  that  of  the  Azores.  In  Asia  there  is  abundant  evi- 
dence of  volcanic  action  on  the  borders  of  the  Mediter- 
ranean, the  Black  Sea,  the  Caspian,  and  the  Persian  Gulr; 
while  along  the  eastern  borders  of  that  continent  there  is  a 
range  not  less  than  5000  miles  in  length  and  250  in  breadth, 


836.  What  analogy  between  these  and  volcanoes  ? 

837.  How  else  do  the  latter  act  ? 

838.  Describe  the  volcanic  range  in  different  countries. 


EARTHQUAKES  AND  VOLCANOES.  257 

including  Sumatra,  Java,  the  Eastern  Moluccas,  and  the 
Phillipiue  Islands;  the  same  range  bearing  farther  north- 
ward, though  less  distinctly,  for  several  thousand  miles,  and 
terminating  in  the  volcanic  cones  of  the  Aleutian  isles.  The 
whole  extent  of  the  two  Americas  is  also  tfa versed  by  a 
volcanic  range,  manifesting  itself  by  eruptions  along  the 
whole  line,  from  the  Rocky  Mountains  through  Mexico  and 
the  Andes,  onward  to  Patagonia  and  Terra  del  Fuego. 
The  islands  of  the  Pacific  iurther  attest  the  presence  of 
similar  forces;  as  do  those — namely,  the  Canaries,  Cape  de 
Verd,  Ascension,  St.  Helena,  Madagascar,  Bourbon,  &c. — 
which  surround  the  continent  of  Africa.  In  these  centres 
of  igneous  action  many  of  the  volcanoes  are  extinct,  others 
are  merely  dormant,  while  many  are  incessantly  active. 

312.  Passing  over  the  disruptions  produced  by  volcanic 
forces,  some  idea  of  their  importance  in  adding  to  the  rocky 
material  of  the  earth's  crust  may  be  gleaned  from  what  is 
stated  in  par.  73,  and  from  the  following  quotations.  In 
the  year  1759  the  plain  of  Malpais,  which  forms  part  of  the 
volcanic  district  of  Mexico,  was  disturbed  from  the  month 
of  June  till  August  by  hollow  sounds  and  a  succession  of 
earthquakes;  and  in  September  flames  burst  from  the 
ground,  and  fragments  of  burning  rocks  were  thrown  to  a 
prodigious  height.  Six  volcanic  cones  were  formed,  of 
which  Jorullo,  the  central  one,  was  elevated  1600  feet 
above  the  plain,  and  continued  burning,  sending  forth 
streams  of  basaltic  lava  till  the  month  of  February  in  the 
succeeding  year.  None  of  the  other  cones  were  less  than 
3JO  feet  in  height.  Twenty  years  after  the  eruption,  this 
spot  was  visited  by  Humboldt,  who  found  around  the  base 
o/  the  cones,  and  spreading  from  them  as  from  a  centre,  a 
m."ss  of  matter  550  feet  in  height,  extending  over  a  space 
of  four  square  miles,  and  sloping  in  all  directions  towards 
the  plain.  A  subsequent  eruption  of  this  volcano  took 

ce  in  1819,  on  which  occasion  the  ashes  discharged 
e  so  abundant,  that  they  covered  the  streets  of  Gua- 

xuato  to  the  depth  of  six  inches,  although  the  distance 


839.  What  three  conditions  of  volcanoes  are  cited  1 

840.  What  historical  incident?  are  named  7 


me 

n;ix 


2/W  GEOLOGY. 

of  that  city  from  the  volcano  is  not  less  than  one  hundred 
arid  forty  miles.  During  the  eruptions  of  Surnbawa  in  1815, 
ashes  were  carried  300  miles  in  the  direction  of  Java,  and 
more  than  200  miles  northwards  towards  the  Celebes,  in 
sufficient  quantity  to  darken  the  air;  they  were  also  found 
floating  in  the  ocean  to  trre  west  of  Sumatra,  a  distance  of 
more  than  one  thousand  miles,  forming  a  mass  two  feet 
thick,  through  which  vessels  with  difficulty  forced  their 
way.  The  last  example  which  we  shall  here  notice  is  that 
of  the  Skaptaa  Jokul,  in  Iceland,  which  took  place  in 
17H3.  This  eruption  continued  with  greater  or  less  ac- 
tivity during  the  space  of  ten  weeks,  and  produced  the 
most  disastrous  effects,  as  well  as  the  most  extensive  geo- 
logical changes,  on  the  face  of  the  island.  "The  immedi- 
ate source,"  says  Mr.  Ansted,  "  and  the  actual  extent  of 
these  torrents  of  rocks  have  never  been  actually  determined; 
but  the  stream  that  flowed  down  the  channel  of  the  Skaptaa 
was  about  fifty  miles  in  length  by  twelve  or  fifteen  in  its 
greatest  breadth.  With  regard  to  its  thickness,  it  was  very 
variable,  being  as  much  as  five  or  six  hundred  feet  in  the 
narrow  channels,  but  in  the  plains  rarely  more  than  a  hun- 
dred, and  often  not  exceeding  ten  feet."  If  such  be  the 
magnitude  of  isolated  and  temporary  eruptions,  the  student 
cannot  fail  to  perceive  how  much  of  terrestrial  change  must 
have  been  produced  by  volcanic  action  even  during  the 
few  thousand  years  of  human  history;  and  can  have  no 
difficulty  in  reasoning  from  modern  igneous  forces  to  those 
which  exerted  themselves  during  the  trappean  and  granitic 
eras.  (See  Appendix.) 

313.  The  products  of  volcanoes  are  commonly  recog- 
nized as  lava,  obsidian,  pumice,  scoriae,  ashes,  mud,  steam, 
and  various  gases,  of  which  muriatic  acid,  carbonic  acid, 
and  sulphuretted  hydrogen  are  the  most  abuudant.  Lava 
i:s  the  name  given  to  the  melted  rock-matter  which  issues 
from  active  craters,  and  which,  when  cooled  down,  foo^ 
varieties  of  volcanic  trap,  as  trachyte,  basalt,  greenstone, 

841.  What  geological  reasoning  is  suggested  ? 

842.  What  are  a'linvdant  products  of  volcanoes  ? 

843.  Explain  each  of  those. 


EARTHQUAKES   AND  VOLCAXpFS.  253 

a:id  <J  lenu-,  aec -rding  to  the  arti-mni  of  felspar,  hor  i- 
b.ende,  and  augite  whicli  UK  se  rooks  respectively  coritaiii. 
Obsidian,  or  volcanic  glass,  is  a  glassy  lava  of  a  black 
colour,  nearly  opaque,  and  scarcely  distinguishable  from 
artificial  glass  slag.  Pumice  is  a  light,  porous,  or  vesicular 
rock,  the  vesicles  having  been  formed  by  the  disengagement 
of  gases  while  the  mass  was  in  a  state  of  fusion.  Scoria, 
cinders,  ashes,  and  the  like,  are  of  the  same  mineral  com- 
position as  the  solidified  lava,  and  seem  to  be  produoed  by 
the  dissipation  of  the  liquid  mass  by  the  explosive  energy 
of  steam  and  other  gaseous  forces.  The  admixture  of  water 
with  volcanic  ashes  forms  a  fetid  clayey  mud,  which  some- 
times bubbles  out  from  fissures,  or  is  ejected  in  currents 
with  considerable  violence.  Gaseous  products  are  in  con- 
tinual exhalation  from  active  craters,  or  from  rents  in  ex- 
tinct volcanoes.  Steam  is  the  most  abundant  of  these; 
and  next  in  order  are  the  sulphurous  vapours,  from  which 
are  derived  those  deposits  of  sulphur  so  extensively  em- 
ployed in  the  useful  arts.  The  manner  in  which  the  rock 
products  arrange  themselves  is  highly  instructive,  inasmuch 
as  it  supplies  the  geologist  with  data  to  reason  respecting 
the  occurrence  of  igneous  rocks  in  connexion  with  the  older 
stratified  systems.  Lava  issuing  from  active  craters  descends 
in  currents  from  the  mountain  side,  filling  up  valleys,  dam- 
ming rivers,  covering  plains,  and  if  in  the  neighbourhood 
of  the  sea,  spreading  along  its  bottom,  there  in  turn  to  be 
covered  by  newer  sediments.  Scoriae,  ashes,  and  other 
light  material  being  showered  abroad,  and  borne  by  winds 
often  to  a  great  distance,  are  scattered  indiscriminately 
over  land  and  sea,  forming  layers  of  considerable  thickness, 
which  under  the  waters  are  also  covered  by  other  deposits. 
Lava  cools  irregularly;  in  one  place  presenting  trachyte  of 
a  porphyritic  texture,  at  another  passing  into  granular  green- 
'stone,  and  not  unfrequently  assuming  a  true  basaltic  struc- 
ture. In  all  this  the  student  must  see  repeated  the  same 
processes  by  which  the  granitic  and  trappean  compounds 
were  formed,  the  same  modes  of  arrangement  and  relation 
to  the  stratified  rocks;  and  so  can  reason  with  certainty, 


Ml.   Wint  variety  results  from  the  lava  cooling  1 


203 

from  what  is  recent  and  apparent,  to  that  which  is  ancient 
and  obscure. 

314.  The  cause  of  volcanoes,  earthquakes,  and  other  sub' 
terra/teem  movements  has  been  the  subject  of  several  theories, 
Lut  is  yet  by  no  means  very  satisfactorily  determined.  The 
most  prevalent  opinion  is  that  which  connects  them  with 
<  ne  great  source  of  central  heat — the  residue  of  that  incan- 
descent state  in  which  our  globe  originally  appeared.  By 
this  hypothesis  it  is  assumed  that  the  crust  of  the  earth  is 
«  f  various  thickness,  that  it  contains  vast  caverns,  and 
is  extensively  fissured — primarily  by  unequal  contraction 
from  cooling,  and  subsequently  by  subterranean  agitations. 
Through  these  fissures  water  finds  its  way  to  the  heated 
mass  within  ;  this  generates  steam  and  other  gases,  and 
these  exploding,  and  struggling  to  expand,  produce  earth- 
quakes and  agitations,  which  are  rendered  more  alarming 
by  the  cavernous  and  broken  structure  oi'the  crust,  and  the 
yielding  material  upon  which  it  rtsts.  Occasionally,  these 
vapours  make  their  way  through  fissures  and  other  aper- 
tures as  gaseous  exhalations,  or  as  hot  springs  and  jets  of 
steam  and  water,  like  the  geysers  of  Iceland.  Oti  the  other 
hand,  when  the  expansive  forces  within,  become  so  power- 
lul  as  to  break  through  the  earth's  crust,  discharges  of  lava, 
red-hot  stones,  ashes,  dns',  steam,  and  other  vapours  follow; 
and  repeated  discharges  of  solid  material  gradually  form 
volcmic  cones  and  mountain  ranges.  It  does  not  follow, 
however,  that  volcanic  discharges  must  always  take  place  at 
the  point  where  the  greatest  internal  pressure  is  exerted, 
for  volumes  of  expansive  vapour  press  equally  upon  the 
crust  and  upon  the  fluid  mass  within,  so  that  the  latter  wi!l 
be  propelled  towards  whatever  craters  or  fissures  do  already 
exist.  This  theory  of  central  heat  is  further  supported  by 
the  occurrence  of  igneous  phenomena  in  all  regions  of  the 
globe,  and  by  the  fact  that  most  volcanic  centres  are  iif 
intimate  connexion  with  each  other — a  commotion  in  one 
district  being  usually  accompanied  by  similar  disturbances 

815    What  of  the  cause  of  subterranean  movements? 

846.  How  are  earthquakes  explained  ? 

847.  How  are  volcanoes  accounted  for  ? 

84S.   What,  igneous  phen'^ienn  prove  central  heat? 


rARTHQt-AKF.S  AVT>  VOLCANOES.  261 

in  another.  The  only  other  hypothesis  which  has  met  with 
countenance  from  geologists,  is  that  which  supposes  the 
internal  heat  to  be  the  result  of  chemical  action  among  the 
materials  composing  the  earth's  crust.  Some  of  the  metal- 
lic bases  of  the  alkalies  and  earths,  as  potassium,  the  mo- 
ment they  touch  water  explode,  burn,  melt,  and  become 
converted  into  red-hot  matter  not  unlike  certain  lavas.  This 
fact  has  given  rise  to  the  supposition  that  such  bases  may 
exist  within  the  globe,  where,  water  finding  its  way  to  them, 
they  explode  and  burn,  fusing  the  rocks  among  which  they 
occur,  creating  various  gases,  and  producing  caverns,  fis- 
sures, eruptions,  and  other  phenomena  attendant  upon 
earthquakes  and  volcanoes.  As  yet,  our  knowledge  of  the 
earth's  crust  at  great  depths  is  excessively  limited;  we  know 
little  of  the  chemical  and  magnetic  operations  which  may 
be  going  forward  among  its  strata,  and  we  are  equally  igno- 
rant of  the  transpositions  which  may  take  place  among  its 
metallic  and  earthy  materials;  but  judging  from  what  we 
do  know,  this  theory,  however  ingenious,  seems  by  no 
means  adequate  to  the  results  produced.  It  is  true  that 
there  occurs  nothing  among  the  products  of  volcanoes  at 
variance  with  its  assumptions;  but  the  magnitude,  the  uni- 
versality, and  the  perpetuity  of  volcanic  action  point  to  a 
more  stable  and  uniform  source — that  source  being  the 
internal  heat  or  residue  of  that  igneous  condition  in  which 
our  planet  originally  appeared. 

EXPLANATORY    NOTE. 

OBSIDIAN — so  named,  according  to  Pliny,  from  Obsidius,  who  first 
found  it  in  Ethiopia.  It  is  a  true  volcanic  glass,  of  various  colours,  but 
usually  black,  and  nearly  opaque.  In  Mexico  and  Peru  it  is  occasion- 
ally manufactured  into  adzes,  hatchets,  and  other  cutting  instruments, 
or  fashioned  into  ring-stones.  So  closely  does  it  resemble  the  black 
slag  of  our  glass  furnaces,  that  in  hand  specimens  it  is  almost  impos- 
sible to  distinguish  the  artificial  from  the  natural  product.  Obsidian 
consists  chemically  of  silica  and  alumina,  with  a  little  potash  and  oxide 
of  iron. 

SULPHUR,  also  known  as  brimstone,  is  a  yellow  brittle  mineral  product 
found  in  various  parts  of  the  world,  but  most  abundantly  in  volcanic 

849.  What  of  the  chemical  theory? 

850.  Why  is  it  objected  to  as  improbable  I 

851.  What  of  obsidian  ? 

12 


262  GEOLOGY. 

regions.  For  economical  uses,  it  is  chiefly 'obtained  from  Sicily,  the 
south  of  Italy,  and  the  West  Indies,  though  many  other  districts  could 
yield  a  profitable  supply.  It  commonly  occurs  massive,  and  intermin- 
gled with  earthy  impurities  ;  but  is  sometimes  found  crystallized,  or  as 
an  efflorescence  on  the  sides  of  fissures,  around  hot  springs,  and  other 
subterranean  openings.  The  properties  of  sulphur  are  well  known  : 
it  is  a  simple  combustible,  solid,  non-metallic;  melts  at  the  tempera- 
ture of  226  degrees  ;  emits  a  peculiar  odour  when  rubbed  ;  and  takes 
fire  at  560  degrees,  burning  with  a  dull  blue  flame  of  a  suffocating 
odour.  It  is  extensively  used  in  medicine,  and  for  numerous  purposes 
in  the  arts,  as  in  the  manufacture  of  gunpowder,  matches,  vermilion, 
sulphuric  acid,  &c.  Chemically  speaking,  sulphur  is  a  very  abundant 
product  in  nature,  being  found  in  conjunction  with  iron,  copper,  lead, 
and  most  of  the  metallic  ores,  being  also  widely  diffused  among  the 
earths  and  rocks,  as  well  as  entering  into  the  composition  of  many 
organized  bodies.  Though  our  commercial  supplies  of  the -mineral  be 
principally  obtained  from  volcanic  districts,  yet  it  is  in  the  power  of 
the  chemist  to  extract  it  from  iron  pyrites  (sulphuret  of  iron),  as  stated 
in  par.  229. 

VOLCANOES  which  give  unremitting  or  periodical  evidence  of  their 
being  the  seats  of  subterranean  fire,  are  said  to  be  active;  such  as  have 
been  in  a  state  of  commotion  within  the  historic  period,  but  now  afford 
no  symptoms  of  igneous  action,  are  termed  dormant ;  while  those  con- 
cerning whose  activity  there  is  no  historical  or  traditionary  mention 
are  regarded  as  extinct. 

RECAPITULATION. 

315.  Having  described,  as  fully  as  the  rudimentary  na- 
ture of  this  treatise  will  allow,  the  various  stratified  forma- 
tions, together  with  their  associated  igneous  rocks,  it  may 
be  of  value  now  to  take  a  general  review  of  the  facts  estab- 
lished by  geologists  in  their  endeavours  towards  a  comple- 
tion of  the  history  of  our  planet. 

316.  Whatever  may  have  been  the   constitution  of  the, 
globe  previous  to  the  origin  of  granite,  we  are  warranted  in 
concluding  that  rocks  of  this  class  form  a  floor  or  basis 
upon  which  all  the  stratified  formations  recline.     Among 
the  granitic  rocks  there  is  no  evidence  of  a  sedimentary 
origin,  no  lines  of  stratification,  no  fossils;  all  of  them  are 
massive,  and  highly  crystalline.     They  upheave,  disrupt, 
and  break  through  the  overlying  strata  in  a  manner  which 
leaves  no  doubt  of  their  having  been  produced  by  igneous 

852.  What  is  the  source,  nature  and  uses  of  sulphur  1 

853.  How  many  varieties  of  volcanoes  are  named  ? 

854.  What  is  predicated  of  granitic  rocks? 


2f>3 

fusion ;  and  such  an  origin  is  now  assigned  to  them  by 
almost  all  geologists.  Had  granite  been  a  meie  meta- 
morphic  rock — that  is,  a  product  derived  from  the  fusion 
rf  sedimentary  strata — some  evidence  of  the  fact  must  have 
beeu  furnished  by  enclosed  fragments  of  the  strata,  by  lo- 
calities where  the  fusion  had  not  been  completed,  or  by 
traces  of  sedimentary  lines;  for,  in  true  metamorphic  rocks 
of  the  secondary  period,  some  such  proofs  are  always  pre- 
sent. But  even  supposing  the  fusion  to  have  been  complete 
in  every  part,  there  is  still  the  question — Whence  was  this 
heat  derived?  And  this  leads  the  geological  theorist  back 
to  the  starting  point,  that  our  planet  was  at  one  time  an  in- 
candescent igntou*  mass.  Whether  the  earth  was  originally 
so  formed,  or  was  fused  by  external  heat,  the  result  would 
be  the  same — a  globe  of  molten  matter,  gradually  giving 
oft*  its  heat  to  surrounding  space,  and  cooling  down  so  as 
in  process  of  time  to  be  coated  with  a  solid  stony  crust. 
This  crust  contracting  and  expanding  irregularly,  accord- 
ing as  certain  areas  were  good  or  bad  conductors  of  heat, 
would  produce  rents,  fissures,  elevations,  and  depressions — 
great  in  as  far  as  our  standard  of  judging  is  concerned,  but 
no  more  in  comparison  with  the  bulk  of  the  globe,  than 
the  scoria?  on  the  surface  of  a  glass-blower's  furnace.  As 
this  process  of  refrigeration  went  forward,  the  gases  capa- 
ble of  constituting  the  atmosphere  nnd  water  would  con- 
dense around  and  upon  the  earth — the  latter  occupying  the 
hollows  of  the  crust,  and  undergoing  a  rapid  evaporization, 
both  by  the  internal  heat  of  the  mass  and  the  external  heat 
of  the  sun — and  the  former  constituting  a  medium  for  the 
elaboration  of  vapours,  rains,  and  other  meteoric  pheno- 
mena. Thus  the  various  operations  of  Atmospheric, 
Aqueous,  and  Igneous  agency  were  set  in  motion  to 
modify  the  newly-formed  crust,  and  to  produce  that  long 
series  of  changes  which  it  is  the  province  of  geology  to 
consider.  This  constitutes  the  first  era  of  our  planet — a 


Son.   What  of  the  earth  having  been  an  incandescent  igneous  mass? 
806    What  geological  reasoning  is  here  T 
ho7.  What  of  the  first  era  of  our  planet  ? 


264  r.F.ot/vrv.  . 

period  when  it  was  void  of  those  conditions  necessary  to 
the  support  of  vegetable  and  animal  existence. 

3 1 7.  The  products  of  the  agencies  now  set  in  motion  were 
the  gneiss  and  mica  schist  systems.  The  rains  which  fell 
upon  the  granitic  crust,  the  streams  which  descended  from 
its  mountains,  and  the  rivers  which  cut  their  way  through 
its  gorges  and  valleys,  would  bear  the  abraded  material  to 
the  lakes  and  seas,  there  forming  layers  differing  little  in 
mineral  composition  from  the  granite  whence  they  were 
derived.  At  this  period  the  earth's  surface  must  have  been 
extremely  unstable,  breaking  down  in  some  localities,  and 
being  upheaved  in  others;  so  that  floods  of  molten  granite 
would  occasionally  envelop  the  newly-deposited  strata;  and 
thus  it  is  often  difficult  to  separate  gneiss  from  rocks  of  true 
granitic  character.  In  process  of  time,  however,  the  gra- 
dual refrigeration  of  the  globe  would  render  the  configura- 
tion of  its  crust  more  stable,  and  so  allow  the  sedimentary 
matter  to  be  deposited  not  only  more  regular! v,  but  also 
less  intermingled  with  igneous  effusions.  Such  a  state  of 
matters  we  discover  in  the  mica  schists,  which  are  more 
finely  laminated,  and  more  continuous  in  stratification,  than 
the  subjacent  gneiss.  Of  the  sedimentary  origin  of  gneiss 
and  mica  schist,  no  one  who  has  examined  these  rocks  in 
the  field  can  have  any  doubt ;  even  in  hand-specimens  the 
lines  of  lamination  are  generally  well-marked  ;  the  crys- 
tals of  which  they  are  composed  are  fragmented  and  water- 
worn,  attesting  the  abrading  agency  to  which  'they  had 
been  subjected,  while  in  granite  every  crystal  is  distinct 
and  entire.  It  is  true  that  the  rocks  of  these  two  systems 
are  of  crystalline  texture,  and  must  have  been  subjected  to 
a  very  high  degree  of  heat — a  temperature  sufficient  to 
form  garnet  within  mica  schist,  but  not  so  powerful  as  to 
obliterate  the  lines  of  deposit  in  the  mass.  Another  and 
unobjectionable  evidence  of  their  sedimentary  origin  is 
afforded  by  the  fact,  that  the  litter  system  consists  of  alter- 

858.  How  is  the  origin  of  the  gneiss  and  mica  systems  explained  ? 

859.  What  proves  that  these  rocks  must  have  been  subjected  to  very 

high  degrees  of  fu-at  ? 

860.  What  further  proves  their  sedimentary  origin? 


RECAPITULATION.  265 

nations  of  various  strata,  as  mica,  talc,  and  chlorite  schists, 
crystalline  li-uestone,  and  quartz.  No  vegetable  or  animal 
remains  have  been  found  in  either  system ;  hence  the 
inference,  that  the  earth  at  this  period  was  not  sufficiently 
cooled  down  to  admit  of  organic  development.  This  con- 
stitutes the  second  geological  era — one  during  which  the  dry 
land  and  waters  were  alike  devoid  of  life  and  vegetation; 
an  epoch  of  incessant  subterranean  agitation,  as  is  evi- 
denced by  the  vast  mountain  ranges,  dykes,  veins,  and  other 
effusions  of  granite  by  which  the  sedimentary  strata  are 
elevated  and  contorted. 

318.  The  tra  of  the  clay-slate  and  gravwacke  which  suc- 
ceeded was  one  during  which  important  events  took  place 
in  the  history  of  the  earth.  Mineralogically  speaking,  these 
rocks  present  an  immense  difference  from  those  of  previous 
systems.  Among  them  the  crystalline  texture  is  faint; 
clayey  compounds  are  derived  from  the  decomposed  felspar 
of  the  gneiss  and  granite,  arenaceous  rocks  from  the  quartz, 
and  conglomerates  from  the  pebbles  collected  along  the 
shores  of  the  sea.  Stratification  is  now  abundantly  obvious; 
and  frequent  alternations  of ,  sandstones,  conglomerates, 
shales,  and  limestones  prevail.  All  this  attests  great  diver- 
sity of  action — rivers,  currents,  tides,  and  waves;  deposition 
in  calm  water,  and  accumulations  by  violent  inundations. 
These  rocks  imbed  the  remains  of  lowly-organized  sea- 
wtcds,  of  zoophytes,  and  of  mollusca.  Here  the  geologist 
is,  for  the  first  time  in  the  history  of  the  earth,  presented 
with  organized  forms — beings  governed  by  the  same  laws 
of  vitality  which  now  regulate  plants  and  animate.  These 
organisms,  it  is  true,  are  not  of  a  high  order;  but  they  are 
as  complete  in  their  structure  and  kind,  as  perfectly  adapted 
to  the  conditions  under  which  they  flourished,  as  the  most 
highly-organized  orders  of  existing  nature.  In  all  their 
parts  we  have  abundant  evidence  of  means  to  an  end — 
proofs  of  that  divine  intelligence  from  whom  nothing  su- 
perfluous or  incomplete  ever  emanates.  The  presence  of 


861.  What  marked  difference  in  the  next  system? 

862.  What  of  organized  forms? 

863.  What  geological  reasoning  is  here  ? 


200  GEOLOGY. 

organized  beings  attests  a  great  reduction  of  the  former 
temperature  of  the  globe ;  the  existence  of  a  shallow  sea- 
shore fit  for  the  growth  of  marine  plants;  a  sea-bottom 
adapted  to  the  support  of  corals  and  shell-fish  ;  and  the 
presence  of  lime  and  other  salts  in  the  waters  of  the  ocean, 
fitted  for  the  production  of  such  calcareous  exuvise.  The 
deposition  of  the  clay-slate  and  grauwacke  forms  the  third 
geological  epoch — one  of  comparative  tranquillity  and  rest, 
capable  of  sustaining  sea-weeds,  zoophytes,  and  mollusca, 
but  not  yet  suited  to  the  creation  of  terrestrial  life  or  vege- 
tation. 

319.  The  succeeding  formations — the  Silurian  and  Old 
Red  Sandstone — are  more  decidedly  sedimentary  than  any 
of  the  previous  systems.  They  are  composed  of  sandstones, 
conglomerates,  shales,  clays,  and  limestones,  alternating 
with  each  other  in  such  a  manner  as  to  prove  the  operation 
of  numerous  agents  during  their  deposition.  At  one  season 
the  rivers  seem  to  have  carried  down  mud  and  clay,  at 
another  sand  of  various  fineness ;  in  one  locality  the  waves 
and  currents  produced  pebbly  conglomerates  along  the  sea- 
shore, at  another  laid  down  the  most  impalpable  sand,  on 
which  is  often  left  impressed  the  ripple-mark  of  the  receding 
tide;  along  some  regions  of  the  sea-bottom  certain  lime- 
stones were  precipitated  by  chemical  agency,  in  others  it 
was  accumulated  by  the  operations  of  coral  zoophytes. 
During  the  deposition  of  these  rocks  a  change  was  effected 
upon  the  climate  and  other  atmospheric  conditions  of  the 
dry  land,  so  as  to  enable  it  to  sustain  a  scanty  vegetation ; 
and  here,  for  the  first  time  in  the  earth's  history,  have  we 
evidence  of  land-plants  in  the  remains  of  equis^etums,  ferns, 
and  other  cryptogamia.  The  previous  sea-weeds  become 
more  prolific:  other  genera  are  added  to  the  zoophytes  and 
mollusca;  and  Crustacea  and  Jishes  constitute  a  new  fea- 
ture in  the  Fauna  of  the  globe.  Respecting  the  land- 
plants,  their  remains  are  too  imperfect  to  afford  any  just 
idea  of  the  climate,  composition  of  the  atmosphere,  or  ele- 


864.  What  characterizes  the  next  formations  ? 

865.  What  do  we  find  here  for  the  first  time? 

866.  What  geological  inferences  are  here  stated  7 


RECAPITULATION.  267 

vntion  of  the  land ;  one  thing  only  is  evident,  that  they  are 
chiefly  aquatic,  and  seem  to  have  flourished  in  low  situations 
I  v  the  sides  of  rivers,  whose  waters  bore  their  detached 
fragments  to  the  seas  of  deposit.  On  the  other  hand,  the 
marine  plants  are  much  the  same  in  kind  with  those  of  the 
grauwacke,  only  flourishing  more  abundantly,  to  furnish 
food  to  the  new  increase  of  herbivorous  mollusca.  The 
silurian  seas  seem  to  have  been  crowded  in  some  localities 
with  zoophytes  and  corals,  for  certain  limestones  are  almost 
wholly  composed  of  their  calcareous  secretions;  and  among 
these  radiata,  encrinites  make  their  first  appearance.  New 
and  gigantic  genera  are  added  to  the  shell-fish ;  Crustacea 
are  introduced  in  the  form  of  the  trilobite ;  an  intermediate 
gradation  between  Crustacea  and  true  fishes  in  the  pterich- 
thys,  coccosteus,  and  ccphalaspis ;  and  perfect  fishes  in  the 
hokiptychius,  osteolepis,  and  other  ganoidia  of  the  old  red 
sandstone.  All  this  attests  a  great  advance  in  the  vital 
conditions  of  the  globe— conditions,  however,  differing  so 
much  from  those  which  succeeded,  that  few  of  the  races 
created  to  live  under  them  are  to  be  found  beyond  the 
limits  of  the  strata  then  deposited.  This  constitutes  the 
fourth  period  of  the  world — one  of  ordinary  tranquillity 
during  the  formation  of  the  siiurian  rocks  and  lower  gray 
sandstones  ;  but  still  occasionally  interrupted  by  volcanic 
action,  as  is  evidenced  by  the  interstratification  of  igneous 
tufa  aiinong  sedimentary  compounds.  The  colouring  mat- 
ter of  the  red  sandstones  and  shales  seems  also  to  bear  evi- 
dence of  igneous  disturbance,  but  in  centres  considerably 
removed  from  the  seas  of  deposit.  Whatever  may  have 
been  the  amount  of  volcanic  disturbance  during  the  forma- 
tion of  these  systems,  there  can  be  no  doubt  of  its  violence 
and  extent  towards  their  close,  when  they  were  upheaved 
into  dry  land,  new  mountain  ranges  formed,  the  previous 
strata  further  fractured  and  displaced,  and  the  seas  of  future 
deposit  circumscribed.  And  here  the  student  rr.ust  c-bsc-rve, 
that  the  igneous  products  have  undergone  a  change  in  their 
composition  and  aspect  as  great  as  that  which  subsists  be- 
tween gneiss  and  sandstone.  The  products  of  previous 

•          867.  What  of  the  volcanic  agency  here  1 


268  « 150  LOGY. 

eras  were  granitic ;  now  they  are  chiefly  greenstone,  fel- 
spar, porphyry,  amygdaloid,  and  other  trappea/t  compounds. 
No  two  sets  of  rocks  could  be  more  widely  dissimilar, 
could  afford  evidence  of  a  more  radical  change  in  the  in- 
terior masses  of  the  earth;  and  though  the  former  are  occa- 
sionally detected  piercing  through  secondary  strata,  it  may 
be  received  as  a  general  truth,  that  by  the  close  of  the  old 
red  sandstone  the  true  granitic  era  had  passed  away. 

320.  The  formation  of  the,  carboniferous  system  con- 
stitutes one  of  the  most  peculiar  and  interesting  eras  in  the 
history  of  our  globe.  Its  limestones,  fossil  shell-beds,  sand- 
stones, shales,  clays,  coals,  and  ironstones,  indicate  a  vast 
variety  and  complexity  in  the  causes  concerned  in  their 
production.  Lakes,  estuaries,  and  shallow  seas,  were  the 
theatres  of  deposit ;  gigantic  rivers,  periodical  inundations, 
tidal  currents,  and  waves,  were  the  transporting  agents; 
broad  river  plains  and  deltas  nourished  vegetation;  a  wide 
extent  of  newly-upheaved  continents  furnished  the  rock 
debris ;  and  new  races  of  plants  and  animals  were  called 
into  existence  to  people  the  scene.  Sea-wer.ds,  corallines, 
and  corals,  were  profusely  scattered  along  the  shores  of  the 
ocean — the  latter  in  such  abundance,  as  to  constitute  beds 
of  limestone  lar  more  extensive  than  the  coral  reels  of  the 
Pacific.  Free  radiated  animals,  like  the  star-fish,  were 
abundant;  shell-Jink,  both  fresh-water  and  marine,  swarmed 
in  myriads,  leaving  their  exuviae  to  form  beds  many  feet  in 
thickness;  while  new  genera  of  Crustacea  were  added  to 
those  which  existed  during  the  silurian  era.  Insecis, 
verrnes,  and  other  articulata,  appear  as  a  fresh  i'eature  in  the 
life  of  the  globe  ;  andjishes,  of  the  most  gigantic  and  pre- 
datory orders,  abound  in  the  seas  and  estuaries.  The  latter 
are  all  of  the  ganoid  and  placoid  orders  ;  and,  judging  from 
their  remains,  several  of  them  seem  to  mark  a  passage  from 
true  cartilaginous  fishes  to  sauroid  reptiles.  The  most 
characteristic  organic  development  of  this  period,  however, 
consists  in  the  almost  inconceivable  growth  of  terrestrial 
vegetation,  from  which  were  derived  those  numerous  beds 

868.  What  renders  the  next  formation  important  7 

869.  What  of  the  fossils  of  this  period  1 

S70.  Whence  are  the  immense  beds  of  coal  derived  ? 


RECAPITULATION.  2G9 

of  coal  peculiar  to  the  system.  Judging  from  existing 
nature,  this  vegetation  was  chiefly  of  a  tropical  character — 
p'llms,  pines,  tree-ferns,  cactaceae,  canes,  equisetums,  reeds, 
rushes,  and  allied  orders ;  but  for  many  there  is  no  ap- 
proaching analogue  among  existing  plants.  Most  of  them 
are  of  gigantic  size,  and  indicate  rapid  growth.  Every 
plain,  and  swamp,  and  hill-side  seems  to  have  been  choked 
with  their  luxuriance,  thus  evincing  conditions  of  tempera- 
ture, moisture,  soil,  &c.,  more  favourable  to  vegetable 
growth  than  the  world  has  ever  since  experienced.  Still, 
however,  with  all  this  verdure — this  diversity  of  hill  and 
plain,  river,  lake,  and  estuary — this  exuberance  of  marine 
li  e,  the  earth  was  a  luxuriant  desert,  if  we  may  so  speak, 
void  of  terrestrial  vitality.  This  constituted  another  cycle  in 
the  earth's  history — a  period  of  excessive  vegetation,  but 
only  of  ordinary  tranquillity,  as  we  find  proofs  of  igneous 
agency  more  or  less  displayed  throughout  the  entire  forma- 
tion. The  subterranean  fires  were,  however,  only  smoulder- 
ing to  renew  their  activity,  to  upheave  into  dry  land  the 
important  products  of  the  carboniferous  strata. 

32.1.  The  era  of  disturbance  which  succeeded  icas  that 
during  which  the  new  red  sandstone  and  magnesian  lime- 
stone were  deposited.  Before  their  commencement,  and 
just  at  the  close  of  the  coal-lbrming  period,  a  magnificent 
displa^  of  subterranean  agency  took  place.  The  hills  upon 
which  the  mountain  limestone  reclines,  the  conical  and 
isolated  elevations  of  the  coal  measures,  together  with  all 
their  fractures,  dykes,  and  upheavals,  were  produced  by 
these  forces.  Every  coal-field  bears  ample  evidence  of  their 
effects  ;  they  seem  to  have  continued  in  activity  over  a  long 
lapse  of  years,  during  which  the  previous  luxuriance  of 
vegetation  passed  away,  together  with  most  of  the  zoophytes, 
mollusca,  and  fishes  which  had  peopled  the  waters.  The 
formation  of  new  strata  was  not,  however,  suspended  by 
these  disturbances;  new  rivers  carried  down  to  new  seas  of 
deposit  sand,  clay,  and  mud  ;  but  the  sandstones  and  shales 
formed  b\  these  materials  are  not  like  those  of  the  coal 


871.  What  charaet.-i-zed  the  next  era  T 
h72.  To  what  agency  are  these  ascnbeil 

!•/* 


270  REOLOCY. 

measures.  They  are  all  highly  coloured,  imbed  few  or  no 
remains  of  plants,  contain  deposits  of  gypsum  and  rock- 
salt,  and  alternate  with  magnesian  limestones.  All  these 
facts  point  to  the  prevalence  of  volcanic  influence — the  red 
colouring  matter,  the  local  aggregations  of  rock-salt,  the 
peculiar  composition  and  texture  of  the  magnesian  lime- 
stone, are  its  immediate  products.  As  these  disturbing 
influences  passed  away,  creative  energy  began  to  be  exerted 
anew;  and  before  the  close  of  the  new  red  sandstone  epoch, 
many  new  genera  of  fishes  and  true  aquatic  reptiles  were 
called  into  being. 

322.  The  period  of  the.  lias,  oolite,  and  chalk  was  one  of 
restored  tranquillity.  The  strata,  with  a  few  limited  excep- 
tions, are  eminently  marine  and  estuary,  deposited  in  quiet 
waters,  and  undisturbed  by  igneous  agitation.  Had  we  a 
map  of  the  globe  at  this  epocn,  it  would  present  a  number 
of  islands  and  low  continents  surrounded  by  comparatively 
shallow  seas ;  the  land  supporting  a  tropical,  but  by  no 
means  exuberant  vegetation,  and  the  waters  swarming  with 
shell-fish,  fishes  and  reptiles.  An  atmosphere  such  as  we 
now  enjoy,  a  tropical  temperature,  and  abundance  of 
moisture,  were  the  conditions  under  which  new  tribes  of 
palms,  ferns,  cycadeae,  conifera,  and  a  few  dicotyledonous 
trees  flourished;  and  under  which  chambered  shells,  naked 
cephalopods,  sea-urchins,  star-fishes,  new  bivalves,  Ctenoid 
and  cycloid  fishes,  numerous  gigantic  reptiles,  marsupial 
mammalia,  and  monkeys,  were  called  into  existence.  In 
all  these  forms  we  discover  a  nearer  approach  to  existing 
nature  than  was  made  by  the  Fauna  and  Flora  of  previous 
eras ;  and  yet  few,  if  any  of  the  genera  outlived  the  chalk 
formation.  The  deposition  of  the  oolitic  and  cretaceous 
systems  constitutes  another  epoch  in  the  history  of  our 
planet  during  which  many  of  its  inhabitants  died  out,  and 
were  succeeded  by  other  races  better  adapted  to  its  pro- 
gressive conditions.  The  period  was  eminently  one  of  rest, 
distinguished  only  at  its  termination  by  a  few  local  disturb- 
ances. 


873.  How  did  the  next  era  contrast  vvith  the  former  1 

874.  What  were  its  peculiarities  ? 


RECAPITULATION.  271 

323.  The  tertiary  strata  were  deposited  under  condi- 
tions still  more  closely  allied  to  those  of  the  present  day. 
With  the  exception  of  gypsum  and  certain  limestones,  the 
gravels,  sands,  marls,  and  clays  are  scarcely  distinguishable 
from  those  of  recent  times.  They  seem  to  have  been 
formed  in  estuaries  and  shallow  seas,  which  at  certain 
seasons  were  cut  off  from  the  influence  of  salt  water,  or  at 
least  were  so  situated  that  fresh  water  was  then  the  pre- 
dominating agent.  None  of  the  basins  of  deposit  are  of 
great  extent ;  they  generally  occupy  situations  still  flat,  and 
differing  little  in  point  of  level  or  configuration  from  exist- 
ing seas.  The  earth  at  this  period  appears  to  have  spread 
out  in  vast  savannahs,  abounding  in  verdure,  and  to  have 
been  clothed  with  grasses,  shrubs,  and  trees  scarcely  differ- 
ent from  living  orders.  Mammalia — herbivora  and  car- 
nivora — of  the  most  varied  forms  and  sizes  now  peopled 
the  surface,  in  all  of  which  we  distinguish  the  prototypes 
of  existing  genera.  Birds  are  also  added  to  the  list  of 
terrestrial  inhabitants,  and  such  n^have  been  found  are 
identical  in  form  with  those  now  around  us.  The  shell- 
fish bear  so  close  a  resemblance  to  those  of  the  present  seas, 
tint  many  of  them  are  identical  in  species.  The  fishes  are 
chiefly  of  extinct  genera,  but  otherwise  closely  allied  in 
their  forms  and  mode  of  life  to  modern  families.  Whales, 
walruses,  seals,  turtles,  crocodiles,  are  now  numerous  and 
indubitable;  so  that,  all  things  considered,  the  tertiary  era 
brings  us  to  the  confines  of  existing  conditions.  This 
epoch  was  terminated  by  a  wide-spread  and  general  dis- 
turbance, by  which  the  dry  land  and  ocean  received  their 
present  configuration.  This  disturbance  was  accompanied 
by  an  almost  total  destruction  of  the  terrestrial  Fauna  and 
Flora ;  by  a  decided  change  of  temperature  in  the  regions 
where  the  tertiary  beds  were  deposited  ;  and  by  the  produc- 
tion of  an  accumulation  (diluvium)  over  the  greater  part 
of  Europe  at  least,  which  forms  a  boundary  between  the 
tertiary  and  current  epochs  not  to  be  mistaken.  With  this 
system  the  subterranean  fires  cease  to  discharge  trappean 

875.  How  is  the  era  of  the  tertiary  strata  marked  ? 

876.  Name  iu  peculiarities. 


272  GEOLOGY. 

rocks,  which  had  been  the  invariable  products  of  every 
igneous  agitation  from  the  dawn  of  the  silurian  period.  It 
is  true  that  on  a  small  scale  there  are  many  of  the  tertiary 
traps  undistinguishable  from  the  products  of  modern  vol- 
canoes; but,  judging  them  by  their  general  relations  and 
composition,  there  is  as  wide  a  difference  bettveen  the 
igneous  rocks  of  the  current  epoch  and  the  trap,  as  there 
is  between  the  trap  and  the  older  granite  compounds. 

3*24.  The  current  era  is  that  lithologically  represented  by 
those  superficial  accumulations  of  gravel,  sand,  clay,  marl, 
peat-moss,  shell-beds,  coral-rees,  &c.,  with  which  every  one 
who  moves  beyond  his  own  dwelling  must  be  to  a  certain 
degree  familiar.  Many  of  these  accumulations  are  of  great 
antiquity,  and,  both  in  their  mineral  and  fossil  characters, 
blend  with  the  tertiary  strata.  One  tact  to  be  observed 
respecting  the  whole  of  them  is,  that  they  are  loosely  and 
irregularly  scattered  over  the  surface,  and  have  been  evi- 
dently deposited  since  the  crust  received  its  present  con- 
figuration. Still,  it  imist  be  borne  in  mind  that  there  is  no 
such  thing  as  geological  rest— the  atmospheric,  aqueous, 
igneous,  and  organic  agencies  are  incessant  in  their  opera- 
tions; so  that  what  we  denominate  "an  era,"  is,  in  fact,  a 
mere  series  of  progressive  movements,  whose  results  pre- 
sent as  many  points  of  similarity  as  will  admit  of  their 
being  classed  under  one  category.  Even  since  the  present 
order  of  things  was  established,  great  changes  have  been 
effected  ;  portions  of  dry  land  have  been  submerged,  and 
portions  of  sea-bottom  raised  above  the  waters;  lakes  have 
been  silted  up,  rivers  changed  from  their  courses,  and 
mountains  formed;  while  organic  agency  has  produced 
peal-mosses  and  conl-reefsof  astonishing  magnitude.  We 
have  seen  that  the  Fauna  and  Flora  of  other  epochs  suc- 
cessively died  away  with  the  change  of  conditions  under 
which  they  flourished ;  and  so  the  commencement  of  the 
current  era  was  marked  by  the  creation  of  new  orders  suited 
to  its  peculiar  conditions.  The^e  nre  the  various  races  of 
plants  and  animals  now  existing — subjected  to  the  same 

877.  What  of  the  current  era  ? 

878.  Are  geological  changes  still  transpiring? 

879.  What  geological  reasoning  is  here  ? 


RECAI'Il'ULATIO.V.  273 

laws  ol'  vitality,  but  differing  in  habits,  form,  and  kind  from 
those  of  other  geological  cycles.  Formerly,  the  orders, 
genera,  and  spe<yes  Were  few,  with  an  immense  number  of 
individuals  under  each  species;  now,  individuals  are  less 
numerous,  while  the  species,  genera,  and  orders  are  in- 
finitely more  varied  and  complicated.  As  far  as  can  be 
inferred  from  the  discovery  of  fossils,  there  has  evidently 
been  a  progressive  development,  of  vegetable  and  animal 
life;  not  progressive  in  point  of  perfectitude — for  the 
zoophyte  of  the  silurian  seas  is  as  complex  and  per.'ect  in 
its  structure  as  those  of  the  Pacific — but  progressive  inas- 
much as  higher  and  more  varied  orders  were  successively 
called  into  being.  This  view,  borne  out  by  all  that  has  been 
witnessed  in  the  stratified  systems,  is  confirmed  by  the  cur- 
rent era,  which  claims  for  itself  still  more  highly-organized 
orders  of  being — these  orders  crowned,  moreover,  by  the 
creation  and  distribution  of  MAN.  In  none  of  the  older 
formations  were  found  any  remains  of  man  or  his  works; 
these  are  confined  to  the  most  recent  and  superficial  accu- 
mulations— to  masses  of  volcanic  scoriae,  peat-bogs,  and 
river-sands. 

325.  The  history  of  the  earth  thus  presents  a  long  series 
of  mineral  and  vital  gradations,  as  yet  but  imperfectly  in- 
terpreted by  geology.  The  stratified  formations,  from  the 
gneiss  to  the  existing  surface,  bear  evidence  of  these  grada- 
tions, both  in  their  composition  and  mode  of  aggregation ; 
so  also  do  the  unstratified  rocks — the  granitic,  trappean, 
and  volcanic  compounds — by  the  order  in  which  they  suc- 
ceed each  other.  On  the  other  hand,  plants  and  animals 
rise,  as  it  were,  from  the  simple  zoophyte  to  man  himself, 
appearing  at  successive  eras,  as  new  conditions  permitted 
their  development.  As  system  gradually  merges  into  sys- 
tem, so  the  Fauna  and  Flora  of  one  period  seem  to  live  into 
that  of  another,  there  being  always  certain  races  which 
serve  as  links  of  connexion  between  succeeding  eras. 
This  idea  of  gradation  implies  riot  only  an  incessant  on- 
ward change  among  the  rock  materials  of  the  earth,  but 

8SO.  What  of  the  relations  of  mail  to  this  era  ? 

8dl.  What  geological  theories  are  broached  touching  the  progressive 
history  of  .he  earth  1 


274  GEOLOGY 

also  that  certain  races  of  plants  and  animals  must  be  per- 
petually dropping  out,  as  links  from  the  great  chain  of  ani- 
mated nature.  And  such  is  the  fact  even  with  respect  to 
the  current  era.  The  mammoth  mastodon,  megatherium, 
and  other  huge  pachydermata  which  passed  from  the  tertiary 
to  the  modern  epoch,  have  long  since  become  extinct, 
leaving  their  bones  in  the  clays  and  gravels  of  our  valleys. 
The  elk,  bear,  wild  boar,  wolf,  and  beaver,  are  now  extinct 
in  Britain;  and  what  takes  place  in  limited  regions,  must 
also  occur,  though  more  slowly,  in  wider  continents.  The 
dodo  of  the  Mauritius,  the  dinornis  and  apteryx  of  New 
Zealand,  are  now  matters  of  history ;  and  the  same  causes 
which  led  to  their  extinction  seem  hurrying  onward  to  the 
obliteration  of  the  beaver,  ostrich,  kangaroo,  and  other 
animals  whose  circumscribed  range  of  existence  is  gradu- 
ally being  broken  in  upon  by  new  conditions.  Such  facts 
as  these,  taken  in  connexion  with  the  numerous  superficial 
changes  produced  by  rivers,  lakes,  seas,  peat-beds,  coral- 
reefs,  earthquakes,  and  volcanoes,  have  led  to  speculations 
as  to  the  conditions  which  yet  await  our  planet. 

326.  Respecting  the  future  history  of  the  globe,  it  were 
vain  to    offer   any  conjecture.     Subjected  as  it   is  to  the 
numerous  modifying  causes  previously  described,  we  know 
that  vast  changes  are  now  in  progress,  and  that  the  present 
aspect  of  nature  is  not  the  same  as  that  she  must  assume  a 
thousand  years  hence.     But  what  may  be  the  character  and 
amount  of  these  changes,  what  the  new  conditions  brought 
about  by  them,  or  what  the  races  of  plants  and  animals 
adapted   to  these  conditions,  we  have  nb  means  of  deter- 
mining.    This  only  we  are  assured  of,  that  whatever  vicis- 
situdes   may    affect  the  globe,  they  will   be    tempered  in 
perfect  accordance  with  the  happiness  of  organized  exist- 
ence:  that  Supreme  Intelligence  which  has  maintained  the 
past  will  continue  to  protect  and  superintend  the  future. 

IMPORTANCE  OF  GEOLOGY. 

327.  The  object  of  the  science  being  to  ascertain  the 
n-iinre   of  the    materials  composing  the  earth's  crust,  their 

882.   What  speculations  are  indulged  ? 
8b3.  Name  the  theoretical  uses  of  geology. 


IMPORTANCE    OF    GEOLOGY.  27,> 

mode  of  arrangement,  and  the  causes  producing  that 
arrangement,  il  has  at  once  a  theoretical  and  practical  im- 
portance. The  former  consists  in  thai  impetus  which  it 
giv,  s  to  intellectual  activity,  the  wholesome  discipline  which 
it  confers  on  the  reasoning  faculties,  those  exalted  notions 
of  creation  which  it  conveys,  the  sounder  convictions  of 
man's  relation  to  external  nature  which  it  imparts,  and  in 
the  thousand  proofs  which  it  establishes  of  a  divine  and 
superintending  intelligence.  The  latter,  on  the  other  hand, 
arises  from  the  economical  benefits  which  it  confers  on 
civilized  life:  from  the  aid  which  a  knowledge  of  its  de- 
ductions affords  to  the  arts  of  mining,  engineering,  archi- 
tecture, and  agriculture. 

328.  In  its  philosophical  and  speculative  importance, 
geology  is  second  to  none  of  the  natural  sciences.  Depend- 
ing for  an  accurate  solution  of  its  problems  upon  mechanics, 
chemistry,  botany,  and  zoology,  it  takes  a  wider  range  of 
investigation  than  any  other  individual  science;  indeed,  as 
a  history  of  the  earth,  it  may  be  said  to  embrace  the  total 
field  of  human  research.  Its  study,  therefore,  calls  into 
activity  not  only  the  observing  powers  to  note  what  actu- 
ally occurs,  but  the  reasoning  faculties  to  account  for  the 
source  and  mode  of  occurrence.  It  is  thus  liable  to  be 
encumbered  with  the  absurd  and  fanciful  theories  of  im- 
perfect knowledge — theories,  however,  which  gradually 
disappear  before  the  light  of  more  accurate  observation  and 
sounder  reasoning.  Though  essentially  aided  by  the  other 
sciences,  it  has  not  left  the  assistance  altogether  unrepaid; 
but  has  afforded  numerous  suggestions  to  the  chemist,  and 
thrown  additional  light  on  the  study  of  plants  and  animals 
by  its  peculiar  fossil  forms,  which  replace,  as  it  were,  the 
lost  links  of  vital  gradation.  But  the  discipline  which  it 
confers  on  the  reason  ing  powers  is  further  enhanced  by  the 
intellectual  pleasure  which  its  investigations  afford.  The 
study  of  existing  nature  is  confined  to  what  is  recent  and 
obvious :  geology  takes  a  bolder  flight,  and  reveals  the  suc- 
cessive conditions  of  the  world  to  the  remotest  periods  of 


884.  What  of  its  practical  value  ? 

8S5.  What  reflections  are  made  upon  speculative  geology  f 


276  GEOLOGY. 

time;  and  as  each  era,  with  its  peculiar  forms  of  life  and 
vegetation,  is  unfolded,  what  research  could  be  more  fasci- 
nating or  instructive?  As  in  existing  nature  everything  is 
impressed  with  proofs  of  divine  wisdom,  so  in  the  revela- 
tions of  geology  every  fact  teems  with  evidence  of  the 
ceaseless  agency  of  the  same  upholding  power. 

329.  The  practical  or  economical  vahte  of  the  science 
refers  more  especially  to  the  art  of  mining,  to  the  construc- 
tion of  roads,  tunnels,  canals,  harbours,  buildings,  &c.  and 
to  the  improvement  of  agriculture.  In  mining,  a  know- 
ledge of  geology  is  essential  at  every  step.  If  the  product 
sought  after  be  coal  or  ironstone,  the  geologist  knows  the 
position  which  these  strata  occupy  in  the  crust  of  the  earth, 
the  nature  of  the  rocks  usually  associated  with  them,  the 
kind  of  fossils  imbedded,  and  can  therefore  direct  the  miner 
with  unerring  certainty.  For  want  of  this  aid,  vast  sums 
of  money  have  irorn  time  to  time  been  expended  in  search 
of  these  minerals — the  parties  being  misled  by  fragments 
of  black  schorl  among  the  primitive  rocks,  carbonaceous 
shales  amid  the  grauwacke,  or  by  thin  lignitic  beds  amid 
the  lias  and  oolite.  Now,  the  practised  geologist  knows 
that  coal,  as  a  distinct  formation,  does  not  exist  previous  to 
the  carboniferous  era,  and  therefore  would  have  warned 
against  the  folly  in  sinking  shafts  in  the  clay-slate  or  old 
red  sandstone ;  he  knows,  also,  that  after  the  commence- 
ment of  the  new  red  sandstone,  coal  in  workable  beds 
ceases  to  be  found,  and  that  lignite,  jet,  and  brown  coal 
are  mere  local  and  insignificant  deposits.  Besides  deter- 
mining the  position  in  which  coal,  ironstone,  and  other 
useful  strata  occur,  geology  can  direct  the  miner  through 
all  those  obstructions  occasioned  by  faults,  dykes,  slips,  and 
the  like ;  for  even  these,  irregular  as  they  seem,  bear  cer- 
tain evidence  of  their  direction — upthrow  or  downthrow — 
which  the  experienced  eye  can  readily  detect.  As  with 
the  minerals  of  commerce  which  occur  in  strata,  so  to  a 
certnin  extent  with  the  ores  of  lead,  copper,  tin,  silver,  and 
gold  which  ;>re  found  in  veins  and  lades.  These  veins 


886.  Illustrate  its  economical  importance. 
8y7.  What  further  uses  are  subserved  by  it  T 


MINING  AND   ENGINEERING.  277 

follow  certain  courses  in  relation  to  the  great  axis  of  ele- 
vation with  which  they  are  associated,  are  interrupted  by 
cross  dykes  and  veins,  are  thrown  up  or  down  by  disloca- 
tions— all  of  which  an  experienced  geologist  can  determine 
and  map  out,  so  as  to  save  much  fruitless  waste  of  labour 
and  capital. 

330.  The  importance  of  geology  to  the  civil  engineer  and 
architect  is  so  obvious,  that  the  fact  requires  little  illustra- 
tion. Possessed  of  a  well-constructed  lithological  map,  on 
which  are  delineated  the  various  kinds  of  strata,  their  dip, 
direction,  and  other  particulars,  the  engineer  has  a  safer 
and  cheaper  guide  for  his  direction  than  the  scattered  data 
of  the  boring  rod.  He  sees  at  once  the  nature  of  the  rocks 
through  which  his  work  has  to  pass — whether  common 
road,  railway,  or  canal ;  can  estimate  with  certainty  the 
expense  of  construction,  and  avail  himself  of  minerals 
which  he  knows  must  lie  in  the  vicinity;  while'one  igno- 
rant of  geological  truths  would  blindly  pass  by  such  advan- 
tages. In  fixing  a  line  of  road  or  railway,  the  informed 
engineer  will  avail  himself  not  only  of  facilities  for  present 
construction,  but  calculate,  from  his  lithological  knowledge 
of  the  district,  for  the  future  benefit  of  those  concerned  in 
the  undertaking.  In  the  case  of  canals,  moreover,  where 
retention  of  water  is  indispensable,  the  geologist  can  effec- 
tually aid  in  the  selection  of  a  route,  by  attending  to  the 
nature  and  dip  of  the  strata,  and  to  the  fractures  and  dislo- 
cations to  which  they  have  been  subjected.  He  is  enabled, 
from  his  knowledge  of  the  rocks  and  their  positions,  not 
only  to  prevent  waste  of  water,  but  to  select  a  route  where 
fresh  supplies  can  be  readily  obtained  from  below.  As 
with  roads  and  canals,  so  with  tunnels,  docks,  Artesian 
wells,  and  other  undertakings  commonly  intrusted  to  the 
civil  engineer.  It  is  true  that  such  works  may  often  be 
satisfactorily  enough  completed  without  the  aid  of  geology 
but  undoubtedly  a  knowledge  of  its  deductions  will  materi- 
ally Assist,  by  conferring  a  certainty  and  security  on  what 
would  otherwise  be  a  mere  system  of  trial  and  error.  The 
assistance  which  geology  brings  to  the  architect  is  not  quite 

8»8.  How  is  the  engineei  profited  by  geology  ? 


278  GF.OUMJY. 

so  obvious;  as  actual  experiment  is,  after  all,  the  host  and 
only  test  of  a  rock's  durability.  However,  by  observing  the 
effects  of  weather,  water,  and  the  like,  on  strata  exposed  in 
natural  sections,  he  can  readily  determine  as  to  their  fitness 
for  any  particular  structure*  The  amount  of  waste  experi- 
enced by  ancient  buildings  is  also  another  safe  and  valid 
test ;  and  it  is  the  travelled  geologist,  and  not  the  mere  build- 
er, who  can  point  to  the  locality,  nay,  to  the  very  stratum, 
whence  the  stones  of  these  buildings  were  obtained.  Thus, 
both  directly  and  indirectly,  the  science  is  brought  to  bear 
upon  architecture;  a  fact  fully  appreciated  by  the  legislature 
in  its  appointment  of  a  commission,  composed  in  part  of 
geologists,  to  determine  the  rock  most  suitable  for  the 
structure  of  the  new  houses  of  parliament. 

331.  The  assistance  which  geology  is  calculated  to  confer 
on  the  science  of  agriculture,  constitutes  one  of  the  most 
apparent  features  in  its  economical  importance.  All  fer- 
tile soils  consist  of  two  classes  of  ingredients — organic  and 
inorganic;  the  former  derived  from  the  decomposition  of 
animal  and  vegetable  matter,  the  latter  from  the  disintegra- 
tion of  the  subsoil  or  rocks  beneath.  Without  a  certain 
proportion  of  organic  matter,  no  soil  can  be  fertile;  but  it 
is  equally  true,  that  without  a  due  admixture  of  inorganic 
compounds,  all  attempts  to  improve  it  will  be  fruitless. 
These  compounds  are  chiefly  clay,  lime,  silicious  earth,  and 
magnesia,  with  certain  salts  of  iron,  manganese,  potash,  and 
s;  da — all  of  which  are  obtainable  either  from  the  igneous 
or  sedimentary  rocks,  or  from  the  superficial  accumulations 
formed  by  their  debris;  and  the  farmer  can  at  once  effect 
a  permanent  improvement  on  his  land  by  supplying  the 
particular  ingredient  in  which  his  soil  may  be  deficient. 
To  do  this,  however,  he  requires  to  know  not  only  the  com- 
position of  the  most  prevalent  rocks,  but  also  the  precise 
spot  which  they  occupy;  in  other  words,  he  must  be  able 
to  comprehend  the  language  and  delineations  of  a  geologi- 
cal map  of  his  own  country.  Besides  this  admixture  of 
inorganic  substances,  there  are  other  conditions  necessary 

889.  What  light  has  it  thrown  upon  agriculture  7 

890.  Illustrate  this  by  examples. 


AGRICULTURE.  279 

to  fertility  ;  namely,  facilities  for  drainage,  capability  of  re- 
taining moisture,  the  innocuous  nature  of  the  subsoil,  and 
power  of  absorbing  and  radiating  caloric.-  Soil  overlying 
trap  and  limestone  requires  less  drainage  than  that  covering 
the  coal  measures,  saliferous  marls,  or  wealden,  because  the 
former  rocks  are  full  of  fissures  and  joints,  while  the  latter 
are  cfcefly  tenacious  and  unbroken  clays.  Again,  land  of 
itself  dry  and  friable  may  be  rendered  wet  by  springs  which 
arise  along  some  line  of  dislocation.  The  farmer  acquainted 
with  the  deductions  of  geology  would  cheaply  lead  off  these 
springs  at  their  source,  while  he  who  was  ignorant  would 
laboriously  furrow-drain  his  whole  field,  and  find,  alter  all, 
that  his  was  the  less  effectual  method  of  the  two.  Such 
are  mere  indications  of  the  assistance  which  geology  is 
calculated  to  confer  on  agriculture — an  assistance  very  apt 
to  be  overrated,  unless  the  farmer  at  the  same  time  avail 
himself  of  the  discoveries  of  chemistry  and  vegetable  phy- 
siology. 

332.  It  must  not,  however,  be  svpposed  that  the  science  is 
of  practical  value  only  to  the  miner,  engineer,  architect, 
and  agriculturist;  every  individual  is  liable  to  be  more  or 
less  assisted  by  its  deductions.  The  capitalist  who  specu- 
lates in  land,  the  agent  who  effects  sales,  the  statistician, 
traveller,  and  explorer,  may  all  reap  direct  adva'ntage  from 
the  same  source.  Take,  for  example,*a  case  of  emigra- 
tion : — Two  individuals,  possessed  of  equal  capital,  set  out, 
say  to  New  Zealand  or  to  the  Far  West  of  North  America. 
The  one  ignorant  of  geology  fixes  upon  a  locality  charac- 
terized by  the  beauty  of  its  scenery  and  the  fertility  of  its 
soil ;  the  other  skilled  in  the  science  decides  upon  a  long- 
rejected  lot,  of  bleak  and  barren  aspect,  but  rich  beneath 
in  coal,  limestone,  iron,  copper,  or  lead,  which  his  geologi- 
cal knowledge  at  once  enabled  him  to  detect.  The  former 
pays  a  high  price  for  his  land,  and  yearly  toils  over  it  to 
reap  therefrom  a  remunerating  harvest ;  the  latter  obtains 
his  despised  territory  for  a  mere  trifle,  nmkes  his  fortune  in 
the  course  of  a  few  years,  and  when  roads  and  canals  are 

891.  What  other  sciences  are  auxiliary  t 

892.  How  is  the  practical  value  of  geology  to  tne  capitalist  shown  t 


280  UROLOGY. 

constructed  around  liim,  re-sells  his  property  for  fifty  times 
its  original  purchase-money.  Such  instances  are  by  no 
means  of  rare  occurrence.  Even  our  own  country  can  fur- 
nish examples  where  estates,  sold  under  ignorance  of  their 
mineral  value,  brought  only  ten  or  twenty  thousand  dollars, 
for  which,  in  less  than  a  dozen  years  afterwards,  an  offer  of 
ten  times  that  amount  was  rejected. 

333.  The  advantages  resulting  to  civilized  life  fnhn  the 
cultivation  of  geology  must  be  rendered  sufficiently  obvious 
even  by  the  above  hasty  and  imperfect  outline;  and  yet  it 
is  scarcely  half  a  century  since  it  was  recognized  as  a  legi'i- 
rnate  branch  of  natural  science.  Previous  to  that  period  it 
was  obscured  by  absurd  theories,  which  drew  down  upon  it 
the  imputation  of  being  a  visionary  and  dangerous  pursuit; 
now,  by  the  cautious  industry  of  its  cultivators,  it  is  estab- 
lished as  one  of  the  most  important  of  human  acquirements. 
It  is  taught  in  our  schools  and  colleges,  disseminated  by 
treatises  and  from  lecture-rooms,  and  especially  fostered  by 
every  enlightened  government.  Like  most  other  sciences, 
it  has  still  a  wide  field  of  research  before  it,  many  difficul- 
ties to  overcome,  and  prejudices  to  remove  ;  but,  linked  in 
connexion  with  all  that  is  valuable  and  interesting  to  man, 
there  is  little  apprehension  for  the  successful  attainment  «.f 
its  object— a  c  mplere  physical  history  of  the  planet  we 
inhabit. 


S93    How  recently  has  it  come  to  be  appreciated  7 
894.  What  were  the  objections  to  it  anciently  t 


GEOGRAPHICAL    GEOLOGY. 


ASIA, 

SIBERIA. — The  north-east  parts  of  this  immense  region 
present  vast  marshy  plains,  called  steppes  ;  but  its  southern 
districts  are  rich  and  fertile.  The  Ural  and  Altai  Mountains 
contain  numerous  mines,  which  furnish  gold,  silver,  platina, 
lead,  copper,  and  iron,  the  latter  appearing  in  great  quan- 
tities under  the  form  of  lode-stone  ;  also  localities  of  the 
diamond,  topaz,  beryl,  lapis  lazuli,  emerald,  onyx,  quartz 
crystals,  aventurine,  rubellite,  chalcedony,  cornelian,  agates, 
etc.  At  Ekaterineburgh,  are  extensive  iron-works.  The 
general  features  of  the  Uralian  range,  resemble  those  of 
the  Altaian.  The  gold  mines  extend  on  the  eastern  flanks  of 
the  former,  in  a  zone  running  through  six  degrees  of  latitude, 
north  and  south  of  Ekaterineburgh ;  low  ridges  also  run 
north  from  the  great  Altai  chain,  in  the  governments  of 
Yeneseik  and  Tomsk,  where,  over  an  area  of  203,000 
square  miles,  great  quantities  of  that  noble  metal  are  found 
in  the  rocks  and  in  the  sand  and  gravel.  The  most  pro- 
ductive are  the  mines  of  Berezovsk,  which  is  the  only  place 
in  the  Russian  territory,  where  the  workings  are  subterra- 
nean. Generally,  the  gangue  is  coarse  gravel ;  but  aurifer- 
ous veins  also  occur,  inclosed  in  a  bank  of  rock. 

A  ton  of  the  soil  yields  thirty- six  grains  of  gold,  in 
extraordinary  cases,  seventy.  The  auriferous  rocks  include 
granites,  metamorphised  slates,  and  other  igneous  and 
altered  rocks.  There  are  three  localities  of  gold  washings 
in  the  eastern  district: — between  the  Tom  and  the  Ob, 

895.  What  are  the  chief  minerals  of  Siberia  ?  896  How  far  do 
the  gold  mine-  extend  ?  897.  How  many  localities  of  gold  washings 
in  the  eastern  delict? 


2S2  GEOGRAPHICAL    GEOLOGY. 

between  the  Yenisei  and  Tom,  and  between  the  Lena  and 
the  Yenisei.  The  metal  is  here  found  in  ferruginous  gravel 
following  diorite  ;  auriferous  sands  also  cap  the  mountains. 
In  the  auriferous  alluvium,  the  quartzy  fragments  generally 
yield  the  most.  In  the  mines  south  of  Miask,  there  was 
found,  in  1843,  a  lump  of  seventy-eight  avoirdupois  pounds 
weight. 

CIRCASSIA  AND  GEORGIA. — This  is  a  rough  and  rugged 
region,  much  resembling  the  "  Helvetic  Republic."  The 
mountains  tower  to  an  immense  height,  and  present  sum- 
mits covered  with  eternal  snow  ;  while  glens  and  gorges 
wind  into  their  very  heart.  In  them  are  extensive  groups 
of  basaltic  columns.  The  country  in  the  level  parts  is 
exceedingly  fertile,  and,  among  the  mountains,  is  highly 
picturesque.  It  is  very  probable  that  rich  and  extensive 
mines  here  exist.  Near  Tiflis  are  hot  springs. 

TURKEY. — The  most  abundant  rock  in  Syria  and  Pales- 
tine, and  which  forms  the  greatest  part  of  the  mountains 
of  Libarius,  Antilibanus,  Carmel.  Galilee,  and  the  ridges 
stretching  south  from  Lake  Asphaltites  (Dead  Sea),  is  upper 
secondary  limestone,  in  general,  compact,  yellowish  white, 
and  resembling  lithographic  stone.  On  this  Jerusalem  is 
built,  and  of  it  Solomon's  Temple  and  other  edifices  were. 
Mount  Libanus  is  shaped  like  a  horse-shoe,  with  its  opening 
towards  the  north,  and  is  referable  to  the  chalk  formation. 
The  rocks  often  contain  silicious  nodules,  as  also  nodular 
masses  of  hornstone,  passing  into  chalcedony,  and  fine 
petrifactions.  In  the  sandstones,  which  are  highly  ferru- 
ginous, occur  beds  of  asphaltum,  particularly  at  Hermoii 
and  Carmel.  On  this  mountain  lignite  is  found,  and,  near 
the  summit,  a  brittle  bituminous  shale.  On  the  east  flank 
of  Antilibanus,  the  limestone  is  found  with  greenstone  ; 
and  a  vesiculous  basalt  with  olivine.  At  Hawran  the 
same  rock  exists.  In  a  dormant  crater,  five  miles  west  of 
Safad,  basaltic  vesiculous  lava  occurs,  and  a  very  porous 
variety  on  the  north  shore  of  Lake  Asphaltites,  and  the 

898.  What  is  said  of  Circassia  and  Georgia  ?  899.  What  is  the 
most  abundant  rock  in  Syria?  900.  Of  what  formation  is  Mount 
Libanus? 


ARABIA.  283 

ruins  of  Jericho  On  the  borders  of  the  lake,  marly  strata, 
and  a  high  ridge  of  rock  salt,  called  Usdum,  occur. 

That  portion  of  Syria  adjacent  to  the  Mediterranean, 
is  a  fertile  valley ;  the  part  next  hi  order  consists  of  a 
double  range  of  parallel  mountains,  running  from  south- 
west to  north-east,  with  innumerable  cliffs,  narrow  valleys, 
and  ravines ;  the  eastern  is  an  extensive  level  of  rocks  and 
sands.  The  face  of  the  country  in  Asia  Minor  is  mount- 
ainous. The  Taurus  presents  to  view  a  chain  of  snow-clad 
mountains,  stretching  in  a  curve  through  the  whole  land. 
To  the  east  of  Smyrna  is  a  region  called  the  "  burnt  coun- 
try." Here  are  thirty  volcanos  with  many  streams  and 
beds  of  lava.  The  period  of  action  in  them  must  have 
been  very  remote.  The  rivers  of  Lydia  and  other  parts  of 
Asia  Minor,  have  supplied  large  quantities  of  gold.  The 
country  in  the  south-east  part  of  Turkey  is  level,  subjected 
to  constant  inundations.  The  Dead  Sea  is  placed  between 
two  ranges  of  mountains,  and  is  curved.  It  is  1337  feet 
below  the  Mediterranean. 

ARABIA. — This  peninsula  is  divided  into,  1.  Arabia 
Petraea,  or  Hedjaz,  the  north  part  of  which  is  mountainous, 
and,  in  general,  stony,  sandy,  and  barren ;  2.  Arabia 
Deserta,  or  Nedsjed,  which  is,  for  the  most  part,  desert ; 
and,  3.  Arabia  Felix,  or  Yemen,  containing  many  rich 
provinces  on  the  coast.  Granitic  rocks  compose  the  high- 
est peaks  around  the  Red  Sea  ;  as  also  the  mountains  on 
each  side  of  the  Arabian  Gulf.  The  same  contain  por- 
phyry and  greenstone.  At  Akaba,  trap  rocks  occur ;  and 
ancient  volcanic  craters  in  the  same  region.  "  The  valley 
of  the  Jordan,  from  Mount  Libanus  to  the  Red  Sea,  is  a 
fissure,  through  which  volcanic  agency  has  been  active,  and 
the  character  of  the  Dead  Sea,  as  well  as  the  thermal 
springs  on  its  margin,  the  extensive  volcanic  rocks  in  the 
same  region,  the  rock  salt,  and  great  amount  of  bitumen, 
and  the  columnar  and  amygdaloidal  rocks  existing  near 
the  Jordan,  render  it  highly  probable  that  this  igneous 
agency  has  been  exerted  at  some  former  period."  "  The 

901.  What  is  the  face  of  the  country  in  Asia  Minor?     902.  Huw 
is  Arabia  divided  ?     903.  What  is  the  geology  of  the  mountain.-  \ 


4  GEOGRAPHICAL    GEOLOGY. 

compact  limestone  rocks,  which  bound  the  Nile  in  the 
whole  of  Upper  Egypt,  and  extend  far  into  the  Sahara,  as 
well  as  the  West  Ariatic  compact  limestones,  in  the  north  of 
Arabia,  are  in  the  mass  composed  of  the  coral  animalcules 
of  the  European  Chalk."  Mount  Hor  and  Wady  Mousa, 
are  of  the  new  red  sandstone  series,  which  extends  through 
ancient  Petra  to  the  south  of  Mount  Sinai. 

PERSIA,  BALLOGISTAN,  AND  AFGHANISTAN. — Persia  on 
the  north  part  is  mountainous  ;  in  the  middle  and  south- 
east, sandy  and  desert  ;  in  the  south  and  west,  level.  Bal- 
logistan  consists  of  stupendous  mountains,  and  plains,  and  a 
iew  fine  valleys.  Moraines  occur  on  the  plain  north-west 
of  Ararat ;  and  in  the  mountains  west  of  Ooroomiah, 
granitic  gneiss  is  the  chief  rock,  having  a  dip  from  10d  to 
30°  south-east.  In  the  same  region  limestone,  gray  sand- 
stone, and  conglomerate  with  gypsum  abound,  and  also 
quartz  rock,  which  likewise  exists  in  some  of  the  islands  of 
the  lake,  and  other  parts  of  Persia.  Mountains  of  red  sand- 
stone and  conglomerate  exist  back  of  Fabreez  and  other  parts 
of  the  country.  Near  the  same  town,  also  on  the  plain  of 
Khay,  with  gypsum  and  other  places  along  the  confines  of 
Georgia,  beautiful  rock  salt  is  mined.  The  white  or  yellow 
ish  calcareous  alabaster  of  Tabreez,  deposited  by  thermal 
waters,  is  found  near  Lake  Ooroomiah.  From  the  lake,  the 
saltest  water  in  the  world,  are  carried  great  quantities  of  salt. 
This  lake,  which  is  1400  yards  above  the  sea,  holds  in  solu- 
tion one-fifth  of  its  weight,  and  contains  also  much  sulphu- 
rated hydrogen.  -These  indicate  volcanic  agency  in  those 
regions,  as  well  as  the  sulphur  in  the  soil,  and  the  springs  and 
deposition  of  asphaltum  in  ancient  Assyria.  In  Koordistan 
is  a  hot  sulphur  spring.  The  water  rushes  out  of  a  crevice 
in  a  rock,  and  after  passing  some  twenty  feet,  becomes  a 
branch  of  Khabour.  It  is  as  clear  as  crystal,  and  of  a 
temperature  of  105°  Fah. 

In  the  Kourdish  mountains  is  a  crater ;  and  a  boiling 
spring  on  the  Akhoor  On  the  west  side  of  the  mountains, 
near  the  Tigris,  are  some  salt  springs.  An  enormous 

904.  What  rocks  occur  in  the  mountains  west  of  Ooroomiah  ? 
905.  What  i«  said  of  the  Lake  ? 


TARTARY,  INDIA    AND    THffET.  285 

deposit  of  calc  sinter  occurs  near  the  site  of  Tact-i-Solomon. 
In  Persian  Armenia,  stands  the  stupendous  detached  moun- 
tain, Ararat,  called  by  the  Turks,  Parmak-dahg,  the  finger 
mountain.  It  consists  entirely  of  ancient  lava.  Near  it 
exists  a  dormant  volcanic  crater.  The  marble  in  the  ruins 
of  Persipolis  resembles  lias  with  casts  of  Turbo.  Mines 
of  silver,  copper,  lead,  iron,  arsenic,  and  turkois,  are  found 
in  Persia.  Copper,  lead,  and  silver  are  mined,  and  fifty 
furnaces  in  operation  at  or  near  Tokat.  Thirty  miles  north- 
east of  Tabreez,  there  exists  an  extensive  and  rich  ore  of 
copper,  the  native  copper,  and  the  blue  and  green  carbo- 
nates. Copper,  iron,  and  silver,  are  also  wrought  near 
Samsoun.  In  the  Nestorian  country,  are  mines  of  lead, 
sulphur,  and  orpiment.  The  latter  ore  occurs  in  veins, 
which  run  into  the  body  of  a  high  mountain. 

TARTARY. — Four  grand  systems  of  mountains  intersect 
or  border  on  this  vast  domain:  the  Himala,  Kuen-lun, 
Thian-chan,  and  the  Altai.  The  latter  chain  presents  its 
magnificent  displays  of  the  four  great  divisions  of  the  strati- 
fied rocks  :  primary,  transition,  secondary,  and  tertiary.  In 
these  metallic  deposits  are  numerous.  Of  gold  1 140  Ibs. 
are  annually  derived  ;  and  of  silver  41,992  Ibs.  (See  Si- 
beria.) The  inland  sea  of  Aral  is  salt,  and  has  no  outlet ; 
in  the  vicinity  are  several  small  saline  lakes.  The  central 
part  contains  deserts  of  great  extent.  Volcanos,  active  and 
extinct,  here  occur,  filling  a  space  of  7500  square  miles. 
The  chief  are  :  Pechan,  Ouroumptsi,  Kobok,  Houtcheon,  and 
Aral-toube. 

INDIA  AND  THIBET. — On  approaching  the  Himala  range 
on  the  south,  we  first  come  to  sandstone  of  the  newer 
secondary  series  ;  then,  in  succession,  argillaceous  schist, 
mica  and  talcose  slate,  quartz  rock,  hornblendic  slate,  and 
limestone.  The  summit  is  chiefly  gneiss,  traversed  by 
granite.  Porphyry  traverses  the  mica  slate.  At  the 
base  occur  tertiary  strata,  in  which,  in  Birmah,  have  been 
found  the  bones  of  the  mastodon ;  and  between  the  Sut- 
lej  and  Ganges,  the  bones  of  the  elephant,  mastodon,  hip- 

9*M>.  What  mines  in  Persia?  907.  What  mountains  and  v.Jcauos 
in  Tar  inn  t 

T  a 


286  GEOGRAPHICAL    GEOLOGY, 

popotamus,  rhinoceros,  elk,  horse,  deer,  gavials,  crocodiles, 
sivatherium,  and  the  monkey.  Here  also  diluvium  occurs. 
In  Middle  India,  the  vast  plains  are  composed  mostly ' 
of  clays,  sands,  and  gravel,  with  remains  of  animals  and 
fossil  wood.  Coal  also  exists,  resting  on  granite.  Indostan 
is  composed  chiefly  of  unstratified  rocks,  though  the  strati- 
fied primary  exist  also ;  likewise  extensive  deposits  of 
secondary,  tertiary  diluvium,  and  alluvium.  In  con- 
glomerate arid  alluvium,  diamonds  are  found  in  several 
localities,  principally  at  Golconda,  of  superior  hardness  and 
brilliancy  ;  while  Pegu  produces  beautiful  ruby.  Topaz, 
cornelian,  zircon,  corundum.,  schorl,  garnets,  agates,  jasper, 
amethyst,  cat's-eye,  chrystolHe,  &c.,  are  common.  Gold, 
tin,  iron,  lead,  zinc,  and  rock-salt  occur. 

Thibet  is  an  extremely  mountainous,  rugged,  and  sterile 
country,  of  very  great  altitude.  From  the  bottoms  or 
margins  of  certain  salt  lakes  borax  is  procured.  Mines  of 
copper  and  mercury  are  said  to  be  worked.  From  Slam 
and  Cochin- China  large  quantities  of  gold  are  procured. 
Geologically,  the  Malaya  peninsula  may  be  considered, 
when  divested  of  its  alluvial  fringes,  as  one  continuous  belt 
of  hills  and  mountains,  separated  from  the  Indu-Chinese 
region,  in  lat.  13°  30'  north.  The  zone  of  elevation  con- 
tinues uninterruptedly  ;  the  western  border  being  a  broad 
skirt  of  alluvium :  beyond  this  another  elevated,  zone 
occurs,  succeeded  by  a  second  tract  of  alluvium,  which 
again  is  bounded  by  a  third  elevated  belt.  The  rocks  are 
principally  plutonic  ;  but  considerable  masses  of  sedi- 
mentary matter  occur.  In  Banca,  the  famous  tin  island, 
the  prevailing  stratified  rocks  are  clays  and  sandstones. 
In  Malacca  are  several  thermal  springs.  Iron  ores  in 
the  south  exist  in  vast  profusion  ;  also,  passim.  In  Singa- 
pore much  of  the  iron-masked  rocks,  containing  nearly  60 
per  cent,  of  pure  metal,  is  used  to  macadamize  the  roads. 
It  is  very  probable,  also,  that  the  whole  length  and  breadth 
of  the  land  abounds  in  tin  ore.  In  Junk- Ceylon  and 


908.  What  is  the  geology  of  Indostan  ?     909.  What- is  the  surface 
of  Thibet  and  geology  of  the  Malaya  peninsula  \ 


CHINA,  JAPAN,   M  \L\YSI  A.  2^7 

Phunga,  about  13,000  piculs  are  annually  dug  out  of  the 
goil. 

At  the  two  extremities  of  the  peninsular  zone  of  eleva- 
tion, tin  sand  is  diffused  in  great  quantities,  the  production 
being  60,000  piculs.  Kedah,  Perak,  Linga,  Sinkep,  Salan- 
gor,  and  the  countries  from  Kalatan  to  Pahang,  abound  in 
tin.  In  fine,  the  entire  zone  is  incomparably  the  greatest 
magazine  of  tin  on  the  globe,  whose  existence  was  unknown 
until  1709.  Gold  is  found  principally  disseminated  in  small 
particles  and  streaks  in  quartz.  Like  the  tin  ore,  it  has 
been  seen  only  in  the  disintegrated  state.  Copper,  silver, 
and  arsenic  have  been  detected  in  Banca. 

Ceylon  is  chiefly  stratified  primary  rock.  The  prevail- 
ing rock,  gneiss,  is  associated  with  dolomite,  and  subordinate 
masses  of  quartz  ro?k  ;  granite,  sienite,  and  greenstone 
exist.  Iron  is  the  most  valuable  mineral.  Chiefly  with 
graphite  in  gneiss  occur  the  gems  :  rose  and  yellow  quartz, 
cat's-eye,  topaz,  schorl,  prase,  garnet,  pyrope,  cinnamon- 
stone,  zircon,  sapphire,  spinelle,  and  corundum. 

CHINA. — The  surface  of  this  country  is  diversified  with 
mountains,  valleys,  and  plains,  whose  known  rocks  are, 
granite,  sienite,  porphry,  sandstone,  &c.  The  minerals 
wrought  are,  gold,  silver,  copper,  mercury,  iron,  lead,  tin, 
arsenic,  coal,  and  marble.  The  other  valuable  minerals 
are,  porcelain  clay,  jasper,  rubiefc,  Corundum,  lapis,  lazuli, 
topaz,  jade,  and  agate. 

JAPAN. — But  little  more  is  known  of  the  geology  of  this 
empire  than  the  fact  that  several  volcanos  exist.  Gold, 
silver,  copper,  and  mercury  are  the  chief  metals,  in  the 
working  of  which  the  Japanese  excel.  Sulphur,  coral, 
amber,  porcelain  clay,  and  amber  abound. 

MALAYSIA. — Borneo  is  mountainous  in  the  interior,  but 
low  and  marshy  toward  the  coast.  Primary  formations 
abound,  forming  the  axes  of  the  principal  mountain  chains  ; 
while  the  secondary,  tertiary,  arid  alluvium  occupy  the 
lower  regions.  Volcanos  also  exist.  Diamonds  and  gold 

910.  What  is  the  principal  rock  in  Ceylon  ?  911.  What  are  the 
chief  minerals  of  Ceylon?  91  "2.  What  are  the  known  rooks  and 
minerals  in  Ch  na  ? 


288  GEOGRAPHICAL    GEOLOGY. 

are  the  chief  minerals.  In  the  interior  of  Java,  through 
its  whole  length,  is  an  uninterrupted  range  of  mountains, 
38  of  which  are  large  volcanos,  and  at  their  bases  are  ter- 
tiary deposits  of  limestone,  clay,  and  marl,  with  rock-salt. 
Sulphur  is  here  obtained  in  great  abundance  and  purity. 
Through  the  whole  extent  of  Sumatra  a  chain  of  mountains 
runs  ;  and  between  the  ridges  are  extensive  plains  consider- 
ably elevated  above  the  surface  of  the  maritime  lands. 
Here  also  are  four  volcanos  ;  while  granite,  trap,  limestone, 
and  other  primary  rocks  exist,  as  also  tertiary  clays.  Gold, 
tin,  iron,  copper,  and  lead  abound.  Coal  has  recently  been 
found,  by  a  Siamese  of  Penang,  on  the  south  side  of  Junk- 
Ceylon.  '  The  bed  is  three  feet  thick  ;  and  the  coal  of  a 
blackish  color,  and  very  bituminous.  Banca,  which  con- 
sists of  gneiss  and  mica  slate  with  granite,  abounds  in  tin 
and  copper.  (See  India.)  The  Philippine  and  Moluc- 
cas are  volcanic.  Celebes,  or  Macassar,  contains  primitive 
rocks  ;  gold  is  an  export. 

AUSTRALIA. — This  insular  continent  contains  mountains, 
extinct  volcanos,  and  arid  wastes.  The  coast  for  the  most 
part  is  bold,  rocky,  and  mountainous  ;  the  rocks  which  are 
known  being  granite,  mica  and  talcose  slate,  quartz,  ancient 
limestones  and  sandstones,  coal  formation,  red  marl,  with 
oolite  and  salt  ;  also  porphyry,  greenstone,  amygdaloid, 
clinkstone,  and  serpentine.  Coal,  iron  of  a  pure  quality, 
copper, 'and  lead  abound.  The  Illawarra  coal  region  is  100 
miles  south  of  Newcastle  on  the  coast,  and  is  referable  to 
the  oolitic  period.*  The  Burra  Burra  copper  mine,  in  South 
Australia,  yielded  in  18  months  9841  tons  of  the  ore  ; 
value  <£  150,000.  Gold  has  also  been  recently  found  here, 
and  topaz  and  agate.  Fossil  bones  from  limestone  caverns 
have  been  collected,  and  referred  to  14  species  of  animals 
similar  to  those  living  ;  as  the  kangaroo,  hypsiprimus,  wom- 
bat, dasyurus,  and  elephant. 

*  See  M'Coy  on  the  Fossil  Botany  and  Geology  of  the  rocks  asso- 
ciate •  !  with  the  coal  of  Australia. 


on.  What  is  the  geology  of  Borneo  :>nd  Sumatra?     914.  Whete 
tlu-   bin  ra  Lurra   copper  mine   f^uatrd? 


mi.YNE^I     . F.AHBA    Y.  289 

POLYNESIA. — The  predominant  formations  in  this  vast 
archipelago  are,  the  volcanic  and  the  coral  reefs.  The  coral 
isle?  are  low  and  level,  e.  g.,  Whitsunday,  Elizabeth,  Queen 
Charlotte,  Egremont,  Lagoon,  and  many  other  islets  be- 
tween the  30th  parallels  of  lat.,  usually  being  scattered  in 
a  linear  manner  over  a  great  extent.  The  Dangerous 
Archipelago  is  1200  miles  long;  Maldivas,  480;  and  a 
line  of  reefs  between  Papua  and  Australia  is  700  miles 
long.  The  volcanic  isles  rise  to  a  great  height ;  as  the 
Sandwich,  Friendly,  Gallipagos,  New  Hebrides,  Marque- 
sas, and  Gambler's.  The  shores  of  nearly  all  these  are 
lined  with  coral.  The  South  Shetland  and  Orkney  islands 
consist  of  primitive  rocks,  along  with  those  of  more  recent 
igneous  origin.  Juan  Fernandez  is  all  basaltic  greenstone. 
The  Society  are  of  igneous  rocks ;  such  as  basalt. 


AFRICA. 

BARBARY. — The  southern  part  of  this  region  is  a  sandy 
plain.  From  the  coast  of  the  Atlantic  to  the  borders  of 
Egypt  extends  the  lofty  chain  of  Mount  Atlas,  whose  sum- 
mit is  of  granite,  gneiss,  mica  slate,  and  clay  slate.  Calca- 
reous rocks  chiefly  make  up" the  north  part  of  the  range. 
Secondary  sandstones  and  tertiary  strata  occur,  including 
trap.  In  Algeria  mineral  springs  and  waters  abound  ;  and 
several  mountains  contain  lead  and  copper.  Bona  is  the 
seat  of  the  noted  coral  fishery.  Salt  of  the  best  quality  is 
produced  in  abundance  from  rocks  and  various  sources  of 
salt  water.  Salt  lakes,  or  marshes  and  streams,  appear 
innumerable ;  and  banks  and  mountains  are  met  with. 
The  mines  near  Biskra,  and  five  leagues  west  of  Milah, 
are  imbedded  in  the  cretaceous  fonnation,  and  inexhausti- 
ble. Biled  ul  Gerid  is  sterile  and  sandy.  Tunis  abounds 
with  salt ;  and  mountains  near  the  capital  yield  silver,  cop- 
per, and  lead.  The  eastern  part  of  Tripoli  is  desert  ;  gold 
dust  is  exported.  Barca  is  a  barren  desert.  Gypsum  is 
also  said  to  occur  in  Rarbajy. 

915.  What  formations  predominate  in  Polynesia?      916.  What 
rocks  occur  in  the  Atlas  chain  1 


290  GEOGRAPHICAL    GEOLOGY. 

ZAHARA. — This  immense  expanse  is  but  a  dreary  waste, 
interspersed  with  few  oases.  Some  parts  consist  of  soiJ 
baked  nearly  as  hard  as  marble  by  a  torrid  sun  ;  while 
others  are  covered  with  a  quartzose  and  calcareous  sand, 
which  is  whirled  about  by  every  wind,  and  often  formed 
into  immense  heaps.  Occasionally  rocks  rise  through  the 
sand,  which,  in  the  east  part,  are  sandstone  and  limestone, 
containing  rock-salt  and  gypsum,  and  traversed  by  trap. 
The  rocks  by  the  coast  are  basaltic. 

THE  REGION  OF  THE  NILE. — The  south  part  of  Egijpt 
is  primary  ;  the  feldspar  in  the  granite  and  sienite  being 
red.  To  the  north  of  Syene  (whence  sienite)  we  met  with 
sandstone  of  the  recent  secondary  rocks.  Then  succeeds  the 
limestone  tract,  which  stretches  from  Thebes  south.  Allu- 
vium occupies  the  portion  between  the  Mediterranean  and 
the  plain  between  Kous  and  Esne.  Sands  from  the  Lybian 
desert,  borne  east  by  westerly  winds,  have  formed  on  the 
west  side  of  the  Nile  remarkable  downs  or  moving  sand 
hills.  Since  1243,  the  delta  has  advanced  a  mile  atDami- 
etta  ;  and  the  same  at  Foah  since  the  1 5th  century.  Mines 
of  gold  were  once  wrought  in  Nubia,  and  some  is  exported 
at  the  present  time.  Excepting  the  banks  of  the  river,  the 
country  is  sandy.  Granite,  sienite,  porphry,  sandstone,  and 
limestone  are  known  to  exist.  Abyssinia  is  mountainous ; 
gold  occurs,  arid  salt  abounds.  Salt  is  the  general  medium 
of  commerce  in  Darfoor.  On  the  east  of  the  country  of  the 
Shilluks  gold  abounds.  Copper  mines  are  said  to  exist  in 
Fertit.  The  Jibbel  el  Kumri  are  elevated  15,000  feet  above 
the  sea. 

WESTERN  AFRICA. — To  the  south  of  Zahara,  from  the 
Senegal  to  the  Cape  of  Palms,  gold  is  found  ;  as  also  in  the 
sands  of  the  Gambia,  the  Senegal,  and  the  Niger.  The 
Gold  Coast  in  the  meridian  of  Greenwich  has  long  yielded 
large  quantities  of  gold  dust.  Granitic  mountains  encom- 
pass Sierra  Leone.  Copper,  tin,  lead,  and  iron  occur  in 
Loango,  The  district  in  lat.  6C  south  consists  of  granite, 
sienite,  gneiss,  mica  slate,  clay  slate,  primary  limestone,  aud 

917.  What  b  said  of  Zahara  ?      918.  Give  the  geology  of  Eg ypt. 
919.  What  metaLs  ami  rocks  in  Loango  ? 


SOU  THE  UN  AND  EASTERN  AFRICA.  291 

queenstone.      Salt,  iron,   and  copper    abound  in  Angola. 
Cimbebas  is  desert  on  the  coast. 

SOUTHERN  AFRICA. — Three  chains  of  mountains  run 
through  this  region  parallel  to  the  coast,  the  height  increas- 
ing toward  the  north.  The  rocks  are  sandstone,  gneiss, 
clay  slate,  grauwacke,  and  quartz  rock.  The  first  is  the 
chief  rock  in  the  extensive  table  lands  extending  to  the 
equator.  Its  strata,  usually  horizontal,  give  a  tabular  shape 
to  the  tops  of  the  mountains.  Table  Mountain  is  an  exam- 
ple. Masses  of  granite,  basalt,  pitchstone,  and  red  iron  ore 
protrude  through  these  rocks,  whose  relative  situation  is  the 
same  as  in  Europe.  The  desert  of  Challahengah  lies  on  the 
tropic  of  Capricorn.  Cape  Town  rises  in  the  midst  of  a 
desert,  surrounded  by  black  and  dreary  mountains. 

EASTERN  AFRICA. — The  Lupata  Mountains  extend 
from  the  equator  to  those  in  South  Africa.  Hosambique, 
especially  between  25°  and  22°  south,  is  rich  in  gold,  which 
is  washed  down  by  the  rivers  in  great  quantities,  and 
makes  a  chief  part  of  its  commerce.  Cazembe  yields  iron 
and  copper  in  abundance.  In  long.  33°  10  east,  lat  13° 
iO  south,  lies  the  extensive  salt  lake  Maravi.  Rich  mines 
of  gold  are  worked  in  the  kingdoms  of  Zanzebar.  Azania 
is  sandy  and  hilly ;  gold  is  an  export.  Mountains  bound 
its  coast.  The  surface,  soil,  and  productions  of  East 
strongly  resemble  those  of  West  Africa. 

SOUDAN. — The  surface  is  much  varied  in  elevation. 
Gneiss,  mica  slate,  clay  slate,  horn  blendic  rock,  quartz 
rock,  and  limestone,  traversed  by  granite,  greenstone,  and 
other  trap  rocks,  constitute  the  parts  of  greater  altitude. 
Salt  and  natron  lakes  occur,  and  vast  beds  of  rock-salt  are 
quarried.  Sou-re,  Bambarra,  and  other  places  abound  in 
gold.  Basaltic  columns  occur  at  Goree.  According  to  the 
natives,  Lake  Tchad  runs  into  the  Nile  by  a  subterranean 
passage. 

AFRICAN  ISLANDS. — Most  of  these  are  volcanic,  con- 
sisting of  basalt  or  lava.  Madagascar  is  traversed  by 
a  chain  of  lofty  mountains,  mostly  granitic,  and  rich  in 

920.  What  rocks  in  Southern   Africa?      921.  What   metals   are 
found  in  Cazembe  ?     922    What  rocks  in  Soudan  ? 


minerals.  Bourbon,  contains  a  volcano  constantly  in  ac- 
tion. The  highest  peak  is  10,000  feet  above  the  sea, 
Mauritius  is  chiefly  composed  of  lofty  mountains;  and 
abounds  in  iron.  St.  Helena  presents  to  the  sea  a  per- 
pendicular wall  of  rock,  from  600  to  1200  feet  high. 
Diana's  Peak,  in  the  centre,  rises  2700  feet  above  the  sea. 
The  soil  of  the  Cape  Verde  Ides  is  dry  and  arid ;  and  the 
surface  mountainous.  Fogo,  one  of  them,  contains  an 
active  volcano.  Salt  is  a  chief  article  of  trade.  The 
Canaries  contain  numerous  mountains,  of  which  the  most 
noted  is  the  volcanic  Peak  of  Teneriffe,  12,072  feet  high. 
Madeira  consists  of  a  lofty  mountain  with  many  peaks. 
In  the  Azores,  are  forty-two  active  and  dormant  volcanos* 
and  many  submarine. 


EUROPE. 

ENGLAND — Affords  a  variety  of  scenery :  the  north- 
ern part  is  hilly  ;  the  eastern  coast,  sandy  and  marshy 
in  many  places  ;  and  the  great  Alpine  chain  extends  from 
Cornwall  to  the  extremity  of  Scotland.  The  last  is  com- 
posed of  primary  and  transition  rocks,  and  probably  con- 
nected with  all  the  granite  ranges  of  the  continent.  A 
range  of  calcareous  hills  extend,  in  a  waving  line,  from 
the  western  extremity  of  Dorsetshire,  to  the  eastern  side  of 
Durham.  East  of  this  line  are  no  beds  of  mineral  coal. 
The  unstratified  rocks,  and  the  Cambrian  and  Silurian 
groups,  are  mostly  confined  to  the  western  districts.  The 
part  embraced  between  Orwell  and  Humber  rivers  and 
east  of  the  meridian  of  Greenwich,  and  the  strip  between 
Liverpool  and  Lancaster  bordering  the  sea,  consist  chiefly 
of  alluvial  and  diluvial  soil.  The  vicinities  of  Southampton, 
Cowes,  and  the  Thames,  are  tertiary. 

The  southern  coast,  extending  from  Exmouth  to  Mar- 
gate ;  a  line  drawn  from  Exmouth  to  Birmingham ;  thence 

923.  What  is  the  geology  of  the  African  Islands  ?     924.  How  ninny 
vqlcanos  in  the  Azores  ?     925.  Give  the  geology  of  England. 


ENGLAND.  293 

one  to  Berwick  ;  the  coast  from  Berwick  to  Hull ;  a  line 
drawn  thence  to  Peterborough  ;  thence  one  to  Colchester  ; 
thence  one  to  Reading  ;  and  thence  to  Margate  ;  include 
the  secondary  district,  chiefly  calcareous,  and  partly  covered 
by  tertiary  and  alluvial  depositions.  The  part  between 
Land's  End  and  Bristol,  and  that  between  Bradford  and 
Scotland,  are  transition  and  primary.  The  strip  between 
Exeter  and  Derby,  and  the  part  included  between  Liver- 
pool, Wales,  Huddersfield*  and  Worcester,  consist  of  inter- 
mixed formations  ;  as  also  the  Isle  of  Man.  Cornwall 
abounds  with  rocking-stones ;  and  many  cavenious  parts  of 
the  rocks  yield  "  Cornish  Diamonds."  Steatite  occurs  at 
Lizard  Point  ;  kaolin  is  afforded  by  the  granite  rocks ; 
while  slate  and  marble  are  supplied  from  the  mountain 
range  But  the  chief  treasures  of  this  part  of  the  island 
are  the  ores  of  tin,  copper,  and  lead  ;  besides  which  are  ores 
of  silver,  antimony,  cobalt,  bismuth,  manganese,  zinc,  and 
iron.  Gold  is  occasionally  found  in  the  sands  of  rivulets. 

Rich  mines  of  lead,  copper,  and  zinc,  are  also  found  hi 
the  mountain  limestone  of  other  parts  of  England.  In  the 
mountains  of  Cumberland,  occur  beds  of  red  unctuous  fer- 
ruginous clay  and  iron  stone  ;  in  one  of  which,  above 
Seathwaite,  is  found  the  celebrated  graphite.  The  longest 
mineral  dyke,  that  has  been  traced,  is  the  Cleveland,  ex- 
tending from  Cock  field  to  the  sea,  ten  miles  below  Whitby. 
It  is  about  ten  yards  wide  ;  being  a  dark  greyish  brown 
basalt.  The  transition  limestone  of  the  northern  range  is 
rich  in  mines  of  lead  and  zinc.  Extensive  deposits  of  iron 
often  accompany  the  coal  formation.  Strata  of  the  latter 
extend  from  Berwick-on-Tweed  to  the  Tees ;  thence  to  the 
Air.  Another  coal-field  commences  a  little  north  of  Leeds, 
and  extends  in  breadth,  twenty-five  miles,  and  in  length, 
about  seventy.  Small  coal-fields  are  near  Ashby-de-la- 
Zouch,  Tamworth,  Atherstone,  and  Coventry.  Bordering 
the  sea  in  Cumberland,  is  another  ;  as  also  in  Lancashire, 
Dudley,  and  Wolverhampton,  Somersetshire,  and  Glouces- 
tershire. 

926.  What  minerals  occur?     927.  Where  are  the  principal  coal- 
fields situated  ? 

13* 


291  GEOGRAPHICAL    GEOLOGY. 

,  The  chief  repositories  of  gypsum,  rocksalt,  and  the 
strongest  springs  of  brine,  are  situated  in  the  red  marie  of 
Cheshire  and  Droitwich,  and  the  new  red  sandstone  at 
Northwich.  'Subterranean  forests  occur  on  the  Lancashire 
and  Norfolk  coasts,  and  in  Yorkshire  and  Lincolnshire. 
Thermal  springs  are  in  Bath,  Derbyshire,  and  Somerset- 
shire. At  Matlock  are  two  chalybeate  springs.  In  the 
London  clay,  the  septaria  produces  the  valuable  Roman 
Cement.  Shropshire  abounds  in  lead,  copper,  iron,  lime- 
stone, freestone,  pipe-clay,  bitumen,  and  coal ;  Monmouth- 
shire in  limestone,  coal,  and  iron  ;  Nottinghamshire  in  a 
kind  of  stone  resembling  alabaster  ;  Derbyshire  in  lead, 
iron,  coal,  marble,  alabaster,  millstones,  barytes,  and  fluor 
spar ;  Staffordshire  in  copper,  lead,  coal,  stone  quarries, 
alabaster,  and  limestone  ;  Worcestershire  in  coal  and  salt ; 
Durham  in  coal,  lead,  iron,  quarries  of  marble,  slate,  mill- 
stone, firestone,  limestone,  grindstone,  and  freestone ;  Lan- 
cashire in  cannel-coal ;  Northumberland  in  lead,  coal,  iron, 
salt,  and  limestone  ;  Cumberland  in  coal,  lead,  copper,  iron, 
graphite,  and  lapis  calaminaris  ;  Westmoreland  in  lime- 
stone and  blue  slate ;  Suffolk  in  shell-marl. 

WALES. — This  principality  is  mountainous  ;  the  south- 
ern coast  being  secondary,  and  the  rest,  primary  and 
transition.  In  South  Wales,  adjoining  the  Bristol  Channel, 
lies  an  almost  exhaustless  supply  of  coal  and  ironstone  ;  as 
also  in  the  north-east  border.  Anglesey  abounds  in  copper 
and  sulphur  ;  Caernarvon  in  copper,  lead,  and  blue  slates ; 
Denbigh  in  lead  and  coal ;  Flint  in  lead,  calamine,  coal, 
limestone,  arid  freestone  ;  Montgomeryshire  in  lead,  slate, 
arid  lime ;  Cardigan  in  lead  and  silver  ;  Caerrnarthen  in 
coal,  lead,  and  lime  ;  Glamorgan  in  lead,  coal,  iron,  and 
limestone.  In  North  Wales,  gold  occurs  in  quartz  veins 

SCOTLAND. — The  general  aspect  is  rugged  and  mount- 
ainous ;  and  the  formations,  primary,  transition,  arid  the 
secondary,  as  far  as  the  cretaceous  system,  with  a  covering 
of  superficial  accumulations.  Sutherland  abounds  in  iron- 
si  one,  limestone,  slate,  lead  ;  Inverness  in  limestone,  iron, 

928.    Where    are   the    chief  deposits   of  gypsum   and  rocksalt? 
929.  Give  the  geulogy  of  Wales.     980.  What  tor  mat  loan  in  Scotland  i 


IRELAND.  296 

and  rock-crystal ;  Fife  in  coal,  iron,  salt,  lime,  and  free- 
stone ;  Argyle  in  copper,  lead,  and  iron ;  Aberdeen  in 
manganese,  graphite,  and  quarries  of  granite,  millstone, 
and  limestone ;  Forfar  in  freestone  and  limestone  ;  Perth 
in  gold  at  Glen  Turret  ;  Clackmaiian  in  coal  and  salt ; 
Stirling  in  iron,  coal,  limestone,  and  basaltic  rock;  Edin 
burgh  in  coal,  iron,  limestone,  and  marble  ;  Haddington  in 
coal ;  Ayr  in  coal,  freestone,  limestone,  iron,  copper,  and 
lead  ;  Lanark  in  gold  at  Cumberhead ;  Dumfries  in  coal, 
lead,  freestone,  and  limestone.  Pearls  and  variegated 
pebbles  are  also  included  in  the  mineral  productions  of 
Scotland.  The  Brora  coal,  is  poor,  and  said  to  be  in  oolite. 
The  Hebrides  are  noted  for  unstratified  rocks.  In  Staffa  is 
the  magnificent  cave  of  Fingal,  200  feet  long,  bounded  on 
each  side  by  splendid  basaltic  columns  in  perpendicular 
ranges,  and  roofed  by  the  fragments  of  others.  Rich  mines 
of  lead  and  gold  occur  at  Lead  Hills. 

IRELAND. — Here  on  an  extensive  scale  occur  all  the 
primary,  transition,  and  older  secondary  formations.  Be- 
neath the  trap,  in  succession,  lie  chalk,  green  sand,  lias, 
and  variegated  marls.  The  former  is  often  changed  into 
granular  limestone.  Trap  is  the  feature  of  Ulster — in 
area,  800  square  miles,  in  thickness  545  feet.  Antrim  has 
an  astonishing  work  of  nature — the  Giant's  Causeway, 
consisting  of  a  vast  number  of  perpendicular  pillars  of 
basaltic  rock,  rising  frem  200  to  300  feet  above  the  water. 
Carlo w  of  Leinster  abounds  in  limestone  ;  Kilkenny  in 
coal,  and  quarries  of  white  and  black  marble  ;  Kings  in 
limestone.  The  coal  in  Munster  is  chiefly  anthracite. 
Cork  abounds  in  coal,  iron,  and  lead  ;  Kerry  in  mineral 
waters.  Lead,  silver,  and  salt  are  also  found  in  Ireland  ; 
while  the  copper  mines  of  Allihies,  Coonbane,  arid  Tigrony, 
are  extensive.  Gold  occirrs  disseminated  in  the  beds  of 
the  streams  which  descend  from  the  northern  flank  of 
Croghan  Kinshela ;  and  Ballinvally,  Killahurler,  and  Bal- 
Ititemple,  largely  yield  the  precious  metal  associated  with 
magnetic  iron-stone,  iron-pyrites,  wolfram,  red  and  brown 

'J31.  What  strata  are  found  in  Ireland  ?     932.  Describe  the  Giant's 
933.  Where  does  gold  occur?  ' 


206  GEOGRAPHICAL    OHOLOGY. 

haematite,  manganese,  tinstone,  and  quartz.  Peat  bogs 
occupy  an  area  of  2,000,000  of  acres,  and  a  thickness  of 
from  15  to  25  feet. 

RUSSIA. — The  surface  is  generally  level,  bounded  on  the 
south  by  the  Silesian  and  Carpathian  chains,  and  on  the 
north  by  the  Ural.  These,  together  with  Russian  Laplaud 
and  Finland,  are  primary,  transition,  and" lower  secondary  ; 
yet  tertiary  arid  alluvium  chiefly  predominate  in  the  coun- 
try. Old  and  new  red  sandstone,  with  the  coal  formation 
intervening  ;  lias  and  other  limestones,  with  green  sand  and 
chalk,  also  occur.  The  diluvium  is  a  deposit  of  clay,  sand, 
arid  bowlders,  containing  relics  of  extinct  land  animals,  and 
brought  from  the  north-east.  Plutonic  rocks  are  rare  ; 
though  the  Caucasus  yields  trachyte.  The  tertiary  strata 
correspond  with  those  of  Hungary.*  The  eastern  slope  of 
the  Ural  has  the  greatest  attractions  for  the  miner ;  but  it 
is  towards  the  west  that  it  offers  to  the  geologist  the  most 
complete  and  distinct  stratigraphical  succession.  There  is 
here  a  great  development  of  the  Devonian  system,  and  cop- 
per abounds.  In  the  empire  medicinal  and  saline  springs 
(iron,  copper,  and  silver)  occur,  and  deposits  of  salt  are 
found  in  the  new  red  sandstone  with  gypsum,  while  coal  is 
not  extensive.  In  Russian  Poland  are,  gold,  silver,  cop- 
per, lead,  iron,  and  marble  ;  also  rubies,  diamonds,  crystals, 
and  other  precious  stones.  At  Sandomir  are  mines  of 
vitriol ;  and  in  Riga  iron. 

SWEDEN  AND  NORWAY. — The  former  is,  in  general,  a 
flat  country ;  the  latter,  rough  and  mountainous.  Chalk 
occurs,  and,  in  Sweden,  some  recent  tertiary  strata ;  but 
the  chief  rocks  are  primary,  transition,  and  lower  secondary. 
In  Norway  the  formations  of  syenite  arid  porphyry  are  ex- 
tensive ;  and  the  mountains  are  mostly  gneiss,  with  mica 
and  talcose  slates.  The  diluvium,  however,  resembling 

*  The  geology  of  the  great  north  eastern  angle  is  giren  in  the 
new  work  of  Count  Keyserling,  entitled,  "  Weisenschaftliche  Beo- 
bichtunfjen  aaf  einen  Reise  in  das  Petschor aland,"  with  23  elegant 
4to  plates  of  fossils,  and  two  maps. 

934.  What  formations  in  Russia  ?     935.  What  is  said  of  the  Ural 
range  ?     906.  What  rooks  in  Sweden  and  Norway  ? 


DENMARK. FRANCE.  297 

that  of  New  England,  is  the  most  remarkable.  The  east- 
ern shore  has  risen  from  100  to  200  feet,  and  is  still  rising. 
The  exports  of  Norway  are,  copper,  silver,  cobalt,  iron,  and 
alum ;  while  extensive  quarries  of  porphyry,  granite,  and 
marble  are  worked.  The  iron  usually  accompanies  gneiss. 
The  Swedish  mines  of  silver  (at  Kongsberg),  gold,  and  iron 
are  prolific.  East  Gothland  has  fine  quarries  of  alum,  stone, 
and  marble. 

DENMARK. — The  surface  is  flat  and  l«»w,  the  soil  sandy 
and  marshy,  chiefly  composed  of  weald,  clay,  and  chalk, 
covered  by  tertiary  and  superficial  accumulations.  The 
surface  of  Iceland  is  mountainous,  stony,  and  barren  ;  pre- 
dominant rocks  being  ignigeuous  of  two  epochs  :  1.  that  of 
greenstone  or  dolerite  ;  2.  that  of  modern  volcanos.  The 
Snaefell  Yokul  is  4560  feet  high.  Mount  Hecla,  caldrons 
of  boiling  mud,  geysers,  and  sulphur  springs  are  other  nota- 
bles. The  Feroe  Ides  are  of  ignigenous  rocks,  with  harbors 
faced  with  tremendous  precipices.  They  afford  agate  and 
jasper,  while  the  amygdaloidal  rocks,  as  also  those  of  Ice- 
land^ produce  beautiful  zeolites. 

FRANCE. — The  chief  part  is  one  widely-extended  plain. 
All  rocks  occur.  Diluvium  abounds,  and  is  rich  in  fossil 
extinct  animals,  particularly  the  pachydermata.  There  are 
six  large  tertiary  basins :  chalk,  oolitic  limestone,  and  new 
red  sandstone  form  extensive  tracts  ;  but  the  coal  strata  are 
less  than  in  England.  Cantal  is  noted  for  its  extinct  vol- 
canos ;  the  rocks  being  basalt,  trachyte,  and  tufa.  Brit- 
tany is  hilly,  with  extensive  heaths.  Coal,  iron,  lead,  silver, 
copper,  manganese,  antimony,  vitriol,  alum,  marble,  gyp- 
sum, slate,  flint,  and  burhstone  abound  ;  while  cobalt, 
nickel,  arsenic,  and  tin  also  occur  in  the  Republic.  The 
surface  of  Corsica  is  mountainous ;  the  soil  stony ;  the 
rocks  chiefly  primary  and  transition ;  the  whole  rich  in 
iron,  lead,  copper,  silver,  alum,  saltpetre,  porphyry,  jas- 
per, amianthus,  talc,  emeralds,  &c.  ;  and  the  south  coast 
abounds  in  beautiful  coral.  In  the  valley  of  the  Rhine, 
between  Basle  and  Manheim,  is  a  noted  gold  district. 

937.  Describe  the  surface  of  Denmark  and  Iceland  ?     938.  What 
minerals  in  France  and  Corsica  ? 


298  GEOGRAPHICAL    GEOLOGY. 

SPAIN. — The  surface  is  very  mountainous  ;  arid  usually 
the  axes  of  the  Pyrenees  and  others  are  primary,  transition, 
and  lower  secondary  rocks.  Tertiary  and  recent  secondary 
strata  to  the  chalk  occur  ;  while  middle  secondary  are  often 
of  great  altitude.  Gold,  silver,  lead,  mercury,  iron,  copper, 
antimony,  cobalt,  cinnabar,  graphite,  sulphur,  alum,  ame- 
thyst, agate,  and  chalcedony  are  found.  Marble  and  alabas- 
ter abound  ;  iii  Catalonia  are  117  varieties.  The  same 
district  also  has  beds  of  rock-salt,  and  around  Olot  is  a 
region 'of  extinct  volcanos.  Asturias  abounds  in  coal.  The 
Bahares  are  mountainous.  The  calcareous  rock  of  the 
Gibraltar  promontory  rises  1300  feet  above  the  sea. 

PORTUGAL. — Portuguese  geology  resembles  that  of  Spain. 
There  are  mines  of  coal,  iron,  copper,  tin.  graphite,  mercury, 
and  lead,  and  quarries  of  marble.  St.  TTbes  is  noted  for  its 
salt-works  ;  and  the  sands  of  the  Tagus  are  a  little  auri- 
ierous. 

GERMANY. — Lofty  primary  mountains  bound  it  on  the 
east  and  south-west.  Secondary  strata  are  less  extensive 
than  in  England  ;  yet  most  of  the  fossiliferous  rocks  of  the 
latter  are  in  the  same  relative  position  in  Germany.  Dilu- 
vial detritus  from  Scandinavia  covers  the  tertiary  rocks 
which  form  the  level  of  the  north  ;  and  all  of  four  other 
tertiary  deposits  occur  in  the  United  States  of  Central  Eu- 
rope. Indeed,  near  all  Neptunian  rocks  here  exist.  The 
primary  Hartz  abound  in  silver  copper,  lead,  iron,  zinc, 
sulphur,  vitriol,  salt,  and  coal  ;  and  the  Erzhgeberge  in 
silver,  iron,  copper,  tin,  lead,  cobalt,  bismuth,  and  arsenic. 
Bohemia  abounds  in  gold,  silver,  copper,  tin,  iron,  lead,  and 
mercury  ;  Tyrol  in  salt,  gold,  silver,  and  copper  ;  Wur- 
temberg  (at  Halle)  in  salt ;  Hesse  in  coal,  iron,  and  copper  ; 
Westphalia  in  lead,  iron,  coal,  and  salt ;  Brandenburg  in 
iron  ;  Silesia  in  coal,  copper,  lead,  iron,  antimony,  sulphur, 
nitre,  mercury,  alum,  vitriol,  agate,  jasper,  and  some  gems  ; 
&iyria  in  iron  ;  lllyria  and  Deux  fonts  in  mercury. 

SWISSERLAND. — Here  mountains  tower  to  an  immense 
height,-  between  which  are  extensive  glaciers,  enormous 

940.  What  metals  are  found  in  Spain?     941.  What  mine?  in  Por- 
tugal 1     942.  What  is  the  geology  of  Germany? 


SWISSEKLAND. HUNGARY,   &C. ITALY.  299 

rocks,  frightful  precipices,  terrific  avalanches,  roaming  tor- 
rents, and  fertile  vales.  The  centre  of  the  Alps  is  of  gneiss, 
mica,  hornblendie,  and  talcose  slates,  and  limestone  ;  the 
first  often  becoming  protogine  :  e.  g.,  Mount  Blanc.  On  the 
iiauks  are  deposits  of  new  red  sandstone,  the  oolitic  system, 
and  tertiary  strata,  with  a  covering  of  diluvium.  The  ter- 
tiary rise  from  2000  to  4000  feet  above  the  sea.  The  Alps 
also  contain  granite,  sienite,  porphyry,  and  greenstone. 

HUNGARY,  TRANSYLVANIA,  GALICIA,  CROATIA,  AND 
SCLAVONIA. — Neptunian  and  Plutonic  rocks  here  occur  ; 
the  latter  including  trachyte,  trachytic  porphyries,  tufas, 
and  conglomerates.  Hungary  abounds  in  gold,  silver,  cop- 
per, and  iron  ;  Transylvania  in  gold,  silver,  lead,  copper, 
mercury,  and  tellurium ;  one  solfatara  has  also  been  found  ; 
(jalicia  (at  Wieliczka)  in  salt. 

BELGIUM  AND  HOLLAND. — The  surface  is  nearly  flat, 
and  much  of  it  below  the  level  of  the  sea.  No  rocks  below 
the  transition  occur.  Clay-slate  is  the  oldest  ;  above  this 
are  the  secondary,  one  or  two  tertiary  basins  and  a  coat  of 
diluvium.  Belgium  (chiefly  at  Mons,)  abounds  in  bitumin- 
ous coal  and  anthracite ;  and  Luxemberg  in  iron  mines. 

ITALY. — Italy  has  the  loftiest  mountains  and  most 
beautiful  plains  in  Europe.  The  Appenines  are  of  lime- 
stone ;  though  in  some  parts  are  slate,  euphotide,  and 
gabbro ;  and  the  Sub-Appenine  hills  are  tertiary,  with 
shells  like  those  found  in  the  Mediterranean.  And  the 
whole  chain  evidently  has  been  elevated  some  4000  feet 
since  the  tertiary  formation.  The  Mediterranean  shores  are 
alluvial ;  and  in  the  clefts  and  caves  of  the  rocks  bone 
breccia  is  found.  Marbles  abound  ;  coal  occurs ;  iron, 
silver,  lead,  copper,  have  been  wrought.  Naples  contains 
two  volcanos  and  one  solfatara.  In  Calabria  granite,  gneiss, 
and  mica-slate  exist ;  and  most  of  the  rocks  of  Sicily  are 
secondary  and  tertiary.  The  latter  supplies  Europe  with 
sulphur ;  Cosenza  abounds  with  salt.  In  the  Isle  of 
Sardinia  the  chief  rocks  are  primary,  transition,  and  lower 

943.  What  is  said  of  Swis^erland  ?  944.  What  is  the  surface  of 
Belgium  and  Holland?  945.  Of  what  fi.nriHtion  is  the  Appeuine 
rmie ?  94rt.  What  rocks  in  Sicil? 


GOO  GEOGRAPHICAL   GT:OLOGT. 

secondary ;  Jura  limestone  occurs  ;  as  also  tertiary  strata 
covered  by  diluvium,  with  volcanic  rocks.  Tuscany  yields 
iron,  alum,  vitriol,  marble,  alabaster,  porphyry,  and  min- 
eral waters.  Parma  abounds  in  copper  and  silver  GOTO 
arid  Malta  are  mostly  made  up  of  soft  limestone  ;  the 
Lipari  Isles,  Procida,  and  Jochia  are  of  volcanic  origin, 
the  first  affording  sulphur,  alum,  nitre,  cinnabar,  pumice, 
&c.  Iron  abounds  in  Elba  and  Sardinia. 

TURKEY. — Here  mountains  are  interspersed  with  fine 
extensive  valleys  ;  and  the  geology  is  similar  to  that  of 
Hungary.  W^allachi  abounds  in  fossil  salt  ;  and  its  rivers 
yield  g  Id.  Some  of  the  mountains  are  rich  in  iron  ;  also 
rocks  of  mica,  with  copper  and  talc.  Mount  Pangeus,  was 
once  famed  for  its  mines  of  gold  and  silver.  Marble  and 
potter's  clay  are  found  in  the  islands  of  the  Archipelago. 

GREECE. — In  its  geological  features  is  like  unto  Turkey. 
Of  the  Ionian  Republic,  Zante  has  springs  of  petroleum ; 
and  St.  Maura,  salt. 


NORTH    AMERICA. 

An  immense  chain  of  mountains  stretches  from  north 
to  south,  along  the  Pacific  coast,  through  the  whole  extent 
of  the  Western  Continent  ;  called,  in  South  America,  the 
Andes  ;  in  Guatemala  and  Mexico,  the  Cordilleras  ;  and 
thence  to  the  Polar  Sea,  the  Rocky  Mountains.  Parallel 
to  the  Atlantic,  the  Appalachian  chain  traverses  the  North- 
ern Continent,  forms  the  Indies  of  the  West,  and  joins  the 
Andes  of  Brazil.  Hence  arise  three  great  divisions  :  the 
Atlantic  Slope,  the  Mississippi  Valley,  and  the  Plain  beyond 
the  Rocky  Mountains. 

RUSSIAN  AMERICA,  AND  GREENLAND. — This  desolate, 
barren,  and  almost  unknown  region,  contains  two  remark- 
able mountains  :  St.  Elias  and  Fairweather ;  the  former 
17,900,  the  other,  14,796  feet  above  the  Pacific.  In  the 

947.  What  is  said  of  Turkey  and  Greece  ? '   948.  What  mountain 
chains  in  America?     949.  What  rocks  in  Russian  America? 


THMTTSri    AMERICA.  MOl 

North  part  of  Greenland   are  the  Arctic  Highlands,  and 
cliffs,  with  red  snow. 

BRITISH  AMERICA. — The  Rocky  Mountains,  which  are  a 
continuation  northward  of  the  Cordilleras,  are  primary 
flanked  by  secondary  deposits,  containing  clay  slate,  grau- 
wacke,  and  limestone.  West  of  these  is  a  volcanic  strip, 
the  prolongation  of  a  line  6000  miles  long.  Bowlders  of 
limestone,  granite,  porphyry,  greenstone,  &c.,  are  scattered 
over  most  of  the  northern  region ;  while  clay  slate  with 
a  cover  of  trap  compose  the  Arctic  coast  from  Cape  Lyon  to 
Coronation  Gulf.  Melville  Island  consists  of  sandstone  with 
relics  of  tropic  coal  plants.  All  classes  of  rocks,  except 
tertiary,  are  found  around  Hudson's  Bay.  Low  ranges  of 
mountains,  having  a  south-west  direction,  commence  in 
Labrador,  become  more  elevated  on  the  south  shore  of  the 
St.  Lawrence,  and  form  the  northern  termination  of  the 
Afipalachian  chain.  Between  Labrador  and  the  Hudson 
River,  the  rocks  are  chiefly  primary  ;  but  the  coast  of  the 
former  is  hypersthenic  and  feldspathose  ;  and  along  the  St. 
Lawrence  is  a  deposit  of  black  fossiliferous  limestone.  And 
the  north  part  of  Nova  Scotia  is  secondary  limestone,  with 
trap  above  and  clay  slate  beneath,  and  embracing  gypsum 
and  saline  springs  ;  wliile  coal  measures  intervene  between 
the  slate  and  sandstone.  Coal,  with  grauwacke  and  clay 
slate,  has  also 'been  found  in  the  interior  of  New  Brunswick; 
as  also  in  Cape  Breton.  Iron  also  abounds  in  the  penin- 
sula of  Nova  Scotia.  Primary  rocks  predominate  in  Up- 
per Canada;  but  one  north  of  the  lakes,  and  the  rocks  in 
the  northern  part  of  Lower  Canada,  are  similar  to  those 
on  the  Labrador  coast.  (Gold  has  lately  been  found  in  the 
valley  of  Chaudiere,  a  ton  of  the  raw  material  yielding  $4.) 
On  the  north  side  of,  and  parallel  to,  the  St.  Lawrence,  run 
two  mountain  ranges  ;  one  17,  the  other  200  miles  distant. 
They  develope  themselves  in  Essex  county,  New  York ; 
thence  stretch  to  Kingston,  where  they  connect  with  a  low 
range  which  extends  along  the  shores  of  the  lakes  and  boun- 

950.  What  rocks  are  found  in  British  America?     951.  What  mi- 
nerals occur  here  ?     952.  What  rock*  predominate  in  Canada  ? 


,>!):J  GEOGRAPHICAL    GKOLOGY. 

dary  of  the  United  States  to  the  Rocky  Mountains.  New- 
foundland is  mountainous  and  rugged. 

UNITED  STATED. — The  Appalachian  chain  occupies  all 
New  England,  crosses  the  Hudson,  and  forms  four  parallel 
and  lofty  ranges  of  mountains  in  Pennsylvania,  Maryland, 
Virginia,  the  Carolinas,  and  Tennessee.  The  Allan  iic 
slope  terminates  at  New  York  ;  but  the  Central  Valley 
extends  from  the  Gulf  to  the  Polar  Sea,  and  is  bounded  on 
the  east  and  west  by  primary  rocks.  The  mountainous 
region  east,  of  the  Hudson  consists  of  gneiss,  mica,  and  tal- 
cose  slates,  quartz  rock,  and  limestone,  intersected  and 
upheaved  by  granite,  sienite,  greenstone,  and  porphyry  ; 
except :  fossiliferous  rocks  appear  in  the  east  part  of  Miine, 
pieces  of  transition  rock  containing  anthracite  in  the  east 
part  of  Massachusetts  and  Rliode  Island,  and  new  red 
sandstone  with  protruding  greenstone  in.  the  Connecticut 
Valley.  The  same  primary  range  continues  through  New 
Jersey  and  Pennsylvania.  The  eastern  belt  passes  near 
New  York  City,  Staten  Island,  and  terminates  at  Perth 
Amboy,  where  it  is  covered  by  red  sandstone. 

At  Trenton  it  commences  a  second  primary  band,  90 
miles  wide,  and  parallel  to  the  one  ending  in  Pennsylvania, 
a  trough  of  red  sandstone  intervening.  It  passes  through 
Virginia,  the  Carolinas,  Georgia,  and,  at  the  Alabama 
River,  under  the  alluvium  ;  while  cretaceous  and  tertiary 
strata  cover  its  south-eastern  flank.  A  range  of  Labrador 
feldspar  and  hyperstheriic  rock  joins  that  on  the  west  of 
Lake  Charnplain,  occupies  a  large  tract  south  of  Lake  Su- 
perior, and  probably  reaches  to  the  Mississippi.  Transition 
rocks  rest  on  the  primary  over  most  of  the  valley.  The 
same  red  sandstone,  commencing  in  Nova  Scotia,  forms  a 
wide  belt  below  the  Highlands  ;  and  thence  passes  in  a 
south-east  direction  to  North  Carolina.  Copper  ores,  bitu- 
minous shale  and  limestones,  and  protruding  greenstone  are 
associated  with  the  deposit  as  far  south  as  Virginia. 
There  it  is  very  calcareous ;  brecciated  Potomac  marble 
being  one  of  its  lowest  beds.  The  cretaceous  system  begins 

953.  What  rocks  east  of  the  Hudson  ?     954.  Describe  the  primary 
range.     955.   What  is  the  extent  of  the  cretaceous  system  i 


VMTKD  STATES.  C03 

at  Nantucket,  passes  to  New  Jersey,  and  thence  in  a  wide 
belt  to  Alabama.  It  also  embraces  much  in  .Af&Sts&jgpt, 
7V nttessee,  Arkansas,  arid  Louisiana •;  and  extends  from 
Lake  Eustis  along  the  Missouri  to  Council  Bluffs. 

The  tertiary  group  of  deposits  commences  at  Martha's 
Vineyard  ;  reappears  in  the  south-east  part  of  New  Jersey, 
and  passes  through  the  Atlantic  coasts  of  Delaware,  Mary- 
land. Virginia,  and  North  Carolina  and  interruptedly 
through  South  Carolina,  Georgia,  Alabama,  Mississippi, 
.and  Louisiana.  "  The  post-tertiary  with  shells  of  a  highly 
arctic  character  has  been  recognized  in  New  York,  and 
Canada."  The  tertiary  rocks  are  the  chief  occupants  of 
the  level  portion  of  the  Southern  States  east  of  the  Appa- 
lachian range,  aiid  the  south  part  of  the  Valley.  The 
erratic  blocks  of  Barre  and  Fall  River,  Massachusetts,  the 
bursting  of  Long  Lake  in  Vermont,  the  slide  in  the  White 
Mountains,  and  the  transportation  of  primary  pebbles  on 
the  right  bank  of  the  Mississippi,  are  instances  of  diluvial 
action.  In  Maine,  the  direction  taken  by  the  diluvium 
was  south;  in  Massachussets,  a  few  degrees  east  of  south  ; 
in  eastern  New  York,  the  same ;  in  western,  west  of 
south  ;  parts  bordering  on  Pennsylvania  and  New  Jersey 
varied  some  degrees  west  from  south,  to  south-east ;  and 
near  New  York  city,  north-west  and  south-east ;  the  fos- 
siliferous  region  of  western  New  York  is  strewed  over 
with  bowlders,  from  western  Michigan  and  from  Upper 
Canada  north  of  the  lakes  ;  on  Long  Island,  the  direction 
corresponded  to  the  rocks  ;  in  Virginia,  south-east ;  in  the 
valley  of  the  Missouri  and  Mississippi  south-east  ;  on  the 
Coteau  des  Prairies,  north.  Few  primary  bowlders  are 
found  south  of  Ohio  river. 

The  Delta  of  the  Mississippi  is  the  greatest  alluvial  de- 
posit, being  13,600  square  miles  in  area.  In  these  super- 
ficial accumulations  have  been  found  :  in  New  Jersey, 
Maryland,  South  Carolina,  Kentucky,  and  Mississippi, 
the  elephas  primigenius  ;  in  Connecticut,  New  York, 

956.  What  parts  of -the  United  States  are  tertiary?  967.  What 
course  was  taken  by  the  diluvium  in  the  several  States  ?  958.  What 
01  game  remains  have  been  found  above  the  secondary  fonnatiou? 


304  GEOGRAPHICAL    GEOLOGY. 

Ncic  Jersey,  Ohio,  Indiana,  Virginia,  Kentucky,  Ittis- 
si$sij)pi,  and  most  of  the  western  States,  the  mastodon 
maximus  ;  in  Virginia  and  Kentucky,  the  megalonyx  ; 
in  New  Jersey  and  Kentucky,  the  cervus  arnericanus  ;  in 
Virginia,  the  walrus ;  on  Skiddaway  Island,  coast  of 
Georgia,  the  megatherium  ;  in  Kentucky  and  Mississippi^ 
the  ox,  (several  species.)  Since  the  protrusion  of  green- 
stone, there  are  no  signs  of  volcanic  agency  east  of  the 
Rooky  Mountains  ;  but  thermal  springs  occur  in  the  western 
borders  of  Massachusetts,  Seneca  Falls,  New  Lebanon, 
Saratoga,  and  Ballston,  New  York,  Bath  co.,  Virginia, 
on  the  Wachitta,  Arkansas,  and  in  Buncombe  co.,  North 
Carolina.  The  carboniferous  limestone  extends  northward 
from  Pennsylvania,  to  Falls  of  St.  Anthony,  arid  westward 
to  Fort  Leavenworth.  Gypsum  and  salt  are  always  found 
in  rocks  below  the  coal  beds.  Along  the  south-east  part  of 
the  valley  the  coal  is  generally  non-bituminous ;  but  ac- 
quires bitumen  as  it  recedes  from  the  primary.  Seams  of 
bituminous  coal  have  been  traced  from  Pennsylvania  to 
200  miles  west  of  the  Mississippi,  and  an  outcrop  of  the 
strata  on  the  eastern  flank  of  the  Rocky  Mountains.  The 
gold  range  extends  along  the  Appalachian  chain,  chiefly  on 
its  eastern  slope  from  Maine  to  Alabama. 

Maine  is  generally  either  undulating  or  hilly  ;  and 
about  the  sources  of  the  Kennebec  and  Penobscot,  is 
mountainous.  Mineral  resource — granite  on  the  coast. 

In  New  Hampshire,  the  country,  for  30  miles  from 
the  coast,  is  diversified  with  hill  arid  dale,  rising,  in  the 
interior,  into  lofty  mountains.  Minerals — iron  and  granite. 

The  face  of  the  country  in  Vermont,  when  not  mount- 
ainous, is  generally  undulating.  Minerals — iron,  lead, 
copperas,  marble,  porcelain  clay,  and  gold  occurs  (at  Somer- 
set,) in  the  quartz  traversing  talco-micacious  slate 

The  west  part  of  Massachusetts  is  crossed  by  the  G  reen 
Mountains  ,  east  of  the  Connecticut  it  is  hilly  or  undulat- 
ing, except  the  south-east  coasts,  which  are  level  and 

959.  What  is  the  extent  of  the  carboniferous  lime-stone?  960. 
"Where  do  the  gold  mines  range  1  961.  What  minerals  in  the  New 
England  States  ? 


fXITF.D  STATES.  305 

sandy.  Minerals — (in  Berkshire  co.,  and  other  parts,) 
iron,  primary  and  transition  marbles,  granite,  and  porphyry, 
(in  Worcester,)  anthracite,  (in  Southampton,)  lead,  and  in 
other  parts,  copper  and  tin. 

RJwde  Island,  in  the  north  part,  is  hilly  ;  in  south 
part,  level.  Minerals — iron,  coal,  marble,  and  freestone. 

Connecticut  is  generally  hilly.  Minerals — iron  (chiefly 
in  Litchfield  co.,)  copper,  in  trap  and  new  red  sandstone, 
tin  and  anthracite.  At  Stafford  is  a  mineral  spring. 

New  York,  in  east  parts,  is  mountainous,  near  the 
Pennsylvanian  boundary,  hilly,  and  other  parts  level  or 
undulating.  Minerals — (in  northern  and  other  parts,)  iron, 
(in  Rossie,)  lead,  (in  western  coasts  and  on  Hudson  river,) 
gypsum  and  silver,  tin,  graphite,  coal,  and  marble,  in 
various  places,  as  also  sulphur  and  salt  springs. 

In  New  Jersey,  the  south-east  and  southern  parts  are 
low  and  sandy,  in  the  central  coasts,  undulating,  the  north 
section,  mountainous.  Minerals — iron,  copper,  zinc,  silver, 
and  marble. 

Pennsylvania,  on  the  west  of  the  mountains,  is  hilly, 
on  the  east  it  is  undulating.  Minerals — (in  the  ridges  and 
mountains  of  the  Alleghany  range,  and  between  the  De- 
laware and  Schuylkill,  chiefly,)  coal,  and  (especially  on  the 
Juniata,)  iron. 

The  surface  of  Delaware  is  generally  low,  level,  and 
sandy. 

The  shores  of  Maryland  include  a  low,  level,  and  allu- 
vial country  ;  the  central  and  western  parts  are  hilly  and 
mountainous.  Minerals — (in  Alleghany  co.,)  coal  and 
iron,  and  25  miles  west  of  Baltimore,  gold. 

In  Virginia,  the  alluvial  tract  extends  from  the  ocean 
and  bay  to  the  head  of  tide  water.  The  surface  rises 
gradually  towards  the  interior,  and  then  becomes  mountain- 
ous and  broken.  Minerals — (near  Richmond  and  Wheel- 
ing, and  in  Chesterfield  and  Prince  Edward  cos.,)  coal, 
(18  miles  from  Abingdon,)  rock-salt  and  gypsum,  (in  the 

962.  What  is  the  surface  smd  what  are  the  mineral?  of  the  Middle 
States?  963.  \Vhat  mineral*  are  found  in  Virginia  and  North 
Carolina "' 


306  GEOGRAPHICAL    GEOLOGY. 

primary  strata  from  the  Rappahannock  to  the  Coosa  m 
Georgia  and  Alabama,  also  in  the  ditrital  deposit,)  gold, 
often  accompanied  with  silver,  lead,  and  copper,  the  latter 
is  common  in  trap  and  new  red  sandstone  ;  iron,  lead, 
graphite,  marble,  limestone,  freestone,  porcelain  clay,  and 
chalk  also  abound,  as  also  sulpher,  hot  and  salt  springs. 

North  Carolina,  on  the  seacoast,  is  low  ;  in  the  interior, 
hilly,  in  the  western  part,  mountainous.  Minerals — gold 
and  ircn  abound,  coal  and  lead  occur.  The  veins  of  gold 
are  found  both  in  hilly  and  low  grounds,  and  vary  .  in 
width  from  a  few  inches  to  several  feet  ;  the  best  having  a 
dip  of  45°  to  the  horizon.  This  gold  range  commences  in 
Virginia,  and  extends  south-west  through  North  Carolina 
along  the  northern  part  of  South  Carolina  into  Georgia, 
thence  north-east  into  Alabama  and  Tennessee. 

In  South  Carolina,  the  country  on  the  coast  is  level  for 
100  miles  towards  the  interior,  after  which  is  a  range  of 
sand  hills,  and  beyond  these  it  is  undulating. 

Georgia  is  level  and  marshy  on  the  sea-coast,  and 
mountainous  in  the  north. 

Florida  is  level,  and  not  much  elevated  above  the  sea. 
In  the  wrest  part  it  is  limestone,  and  cavernous  in  its  struc- 
ture. 

Alabama  is  undulating  in  the  south  and  central  parts, 
and  mountainous  in  the  north.  Minerals — coal,  iron,  arid 
gold. 

Mississippi  is  undulating,  containing  several  ranges  of 
hills  of  moderate  elevation. 

Some  parts  of  Louisiana  are  hilly,  others  flat  and 
sandy ;  arid  in  the  south-west  parts  of  the  State  are  exten- 
sive prairies. 

The  eastern  part  of  Arkansas  is  low  and  marshy,  the 
interior  and  northern,  elevated.  The  mountains  contain 
iron,  lead,  coal,  salt,  and  sulphur. 

The  face  of  the  country  in  east  Tennessee  is  bold  and 
mountainous  ;  the  west,  undulating.  Minerals — iron,  lead, 
gold,  gypsum,  burhstone,  white,  grey,  arid  red  marble,  and 

964.  What  minerals  in  Alabama?  965.  What  in  Arkansas  and 
Tennessee  ? 


UNITED  STATES.  307 

nitrous  earth.  Salt  springs,  caves,  petrified  trees,  bones  of 
mammoths,  and  other  organic  relics,  occur. 

Kentucky  in  the  east  part  is  hilly  and  undulating;  in 
the  west,  level.  Beneath  the  mountains  it  rests  on  a  bed 
of  limestone,  usually  8  feet  below  the  surface,  which  the 
rivers  have  excavated  several  hundred  feet  in  depth..  The 
limestone  country  also  abounds  in  subterranean  caves  and 
sink  holes,  the  former  impregnated  with  nitre.  Salt  springs 
also  abound. 

Indiana,  south  of  the  White  and  its  east  Fork,  is  hilly 
and  rough  ;  in  the  north,  level  or  undulating.  Minerals- 
coal,  iron,  lime,  and  salt ;  and  epsom  salts  are  found  near 
Corydon. 

The  face  of  the  country  in  Ohio  presents  a  large  surface 
of  table- land,  sloping  towards  Lake  Erie  on  the  north,  and 
the  Ohio  river  on  the  south.  The  most  hilly  parts  are  in 
the  south-east  and  east  sections,  where  coal  and  salt  abound. 
Iron  is  obtained  in  the  same  regions,  and  also  in  the  west- 
ern reserve  counties.  Gypsum  is  found  near  Sandusky, 
and  limestone,  freestone,  marble,  and  mineral  springs 
abound  in  many  parts. 

Michigan  is  level,  or  gently  rolling.  Copper  and  coal 
abound  ;  the  former  south  of  the  Lake  Superior ;  and 
south  of  this  district  masses  of  the  metal  occur  in  the  di- 
luvium over  an  area  of  several  thousand  square  miles. 
These  fragments  are  derived  from  ores  traversing  greenstone, 
amygdaloid,  and  an  overlying  conglomerate. 

Iowa  is  generally  level,  and  in  the  northern  part  is  a 
high  table-land ;  lead,  coal,  iron,  and  limestone  abound ; 
the  first  embraces  a  strip  of  townships. 

Wisconsin  is  generally  hilly,  with  the  exception  of 
some  prairies,  and  the  north  part  is  mountainous.  Lead, 
copper,  zinc,  and  iron  abound.  The  lead  region  of  this 
part  of  the  United  States  is  87  miles  long  from  east  to 
west,  and  54  broad,  and  is  chiefly  in  "Wisconsin.  At  Mi- 
neral Point,  great  quantities  of  copper  and  zinc  occur. 

Missouri  is  low  and   swampy  in  the  south-east  part. 

966.  What  is  said  of  Kentucky  I  967.  Describe  the  surface  of 
Ohio  ?  968.  W  hat  is  the  extent  ot  the  lead  region  ? 


SOS  GEOGRAPHICAL    GEOLOGY. 

Beyond  the  highlands,  which  mark  the  boundary  of  this 
tract,  the  country  rises  and  extends  to  the  mountainous 
lead  region,  and  the  banks  of  the  Osage,  then  comes  a 
broken  and  hilly  tract,  and  finally,  in  the  western  part,  are 
extensive  prairies.  Minerals — lead  iron,  coal,  salt,  zinc, 
antimony,  graphite,  silver,  copper,  chalk,  and  flint.  The 
deposits  of  specular  iron  ore  are  connected  with  porphyry, 
while  a  stratum  of  granite  with  trap  dykes,  6  miles  in 
width,  separate  them  from  the  mountain  limestone.  Iron 
Mount,  350  feet  high  and  two  miles  in  circuit,  is  entirely, 
and  Pilot  Knob,  600  feet  high  and  three  miles  in  circuit,  is 
partly,  composed  of  this  ore.  The  centre  of  the  lead 
mines  is  from  50  to  70  miles  miles  south-west  of  St.  Louis. 
At  Boone's  Lick,  St.  Genevieve,  and  Herculaiieum,  are 
salt  springs. 

Prairies  cover  two-thirds  of  the  surface  of  Illinois  ;  the 
north  part  is  hilly  and  broken  ;  the  margins  of  the  rivers 
are  usuall  alluvial,  bounded  at  a  short  distance  by  bluffs 
or  banks,  which  at  the  height  of  100  or  150  feet,  spread 
out  into  table-lands.  Coal  is  found  in  nearly  every  county  ; 
and  iron,  copper,  and  chalybeate,  sulphur,  and  salt  springs 
abound.  The  lead  district  occupies  10  townships,  the  ore 
lying  in  horizontal  strata,  and  yielding  75  per  cent. 

Texas,  consists  chiefly  of  vast  prairies,  and  the  mountains 
abound  in  silver,  gold,  and  other  valuable  minerals.  In 
the  southern  part  is  the  Mustang  Desert,  containing  a  salt 
lake  ;  and  a  like  lake  occurs  at  the  head  of  the  Brazos. 
The  northern  part  contains  a  portion  of  the  great 
Desert. 

The  Indian  and  Missouri  Territories  are  vast  wilder- 
nesses, consisting  of  extensive  prairies.  On  the  western 
frontier  rise  the  Rocky  Mountains  to  a  great  height.  A 
few  miles  up  Muddy  River,  (long.  111°,  lat.  4U°,)  Fre- 
mont collected  a  beautiful  series  of  specimens  of  fossil 
ferns,  associated  with  which  were  found  several  beds  of 
coal. 

In  the  mountainous  region  of  Oregon,  occur  many  basaltic 

?69.  What  metals  abound  in  Missouri  ?  970.  What  is  said  of 
H)ii»'ji>?  971  What  i*  th*  extent  of  the  lead  district  in  Illinois  '', 


TTCITED  STATES,  309 

or  volcanic  rocks.  The  whole  country  from  Ctueen  Char- 
lotte's Island  on  the  north,  to  California  on  the  south,  and 
from  the  mountains  on  the  east  to  the  ocean  on  the  west, 
is.  no  doubt,  of  igneous  formation.  The  channel  of  the 
Columbia,  in  many  places,  is  walled  up  on  its '  sides,  and 
studded  with  basaltic  islands,  rising  from  20  to  200  feet  in 
height,  and  the  same  river  passes  through  a  basaltic  mount- 
ain of  more  than  1000  feet  in  height.  Indeed,  the  whole 
is  a  region  of  extinct  volcanoes  ;  for  lava,  trachyte,  basalt, 
massive,  and  columnar,  and  other  volcanic  productions, 
occur  along  many  of  the  rivers  and  other  parts.  Beds  of 
rock-salt  are  found  (particularly  at  the  head  of  Salmon 
River,)  and  epsom  salts  on  both  sides  of  the  Rocky  Mount- 
ains. A  gold  mine  of  great  extent  is  reported  to  exist  in 
this  territory,  lying  in  the  vicinity  of  the  Rocky  Mountains, 
chiefly  on  the  Powhattan  River.  The  metal  is  found  not 
only  in  the  sands  of  the  streams  flowing  from  the  mount- 
ains, but  upon  the  mountains  mixed  with  quartz,  and  in 
the  rocky  strata.  If  this  is  true,  we  have  then  two  gold 
ranges, — one  following  the  Appalachian  chain,  the  other, 
the  Rocky  or  Cordilleras.  It  is  very  probable  also  that 
coal  exists  on  Vancouver  Island. 

California. — We  now  come  to  a  realized  El  Dorado — 
a  veritable  terra  (Toro,  towards  which  the  tide  of  emigra- 
tion is  now  setting  frojn  all  quarters  of  the  earth.  Upper 
California,  or  that  part  of  Western  America  recently  ceded 
to  the  United  States,  is  embraced  between  lat.  32°  and  42° 
north,  and  between  long.  109°  west  and  the  Pacific  Ocean, 
containing  about  400,000  square  miles.  That  part  east 
of  the  Colorado,  whose  southern  boundary  rests  on  the 
Gila,  is  entirely  occupied  by  broken  mountain  ranges,  with 
narrow  valleys  intervening.  The  general  features  of  the 
central  part,  lying  between  the  Colorado  and  the  Sierra 
Nevada,  are  those  of  a  semi-desert,  the  north  part  forming 
a  "  Great  Basin,"  which  is  400  miles  in  extent  from  east 
to  west,  by  250  from  north  to  south,  and  elevated  some 

972  Of  what  formation  is  Oregon  ?  973.  What  volcanic  produc- 
tions are  found  t  974.  What  ie  the  extent  of  California  ?  975. 
Describe  the  Great  Basin  ? 

14 


310  GEOGRAPHICAL 

5000  feet  above  the  ocean,  having  a  succession  of  isolated 
mountain  ranges,  running  north  and  south,  their  general 
outline  being  sharp  and  rugged.*  This  great  valley  con- 
tains the  Great  Salt  Plain,  which  is  40  miles  broad,  and 
1 50  long,  with  a  snow-like  incrustation  of  saline  and  alka- 
line bodies,  and  very  compact  and  hard  on  its  eastern  bor- 
der. The  crust  is  from  \  to  .'  an  inch  thick,  beneath  which 
is  a  stratum  of  damp  whitish  sand  and  clay  intermingled  ; 
fragments  of  "  white  shelly  rock"  are  strewn  over  the  en- 
tire plain,  arid  imbedded  in  the  salt  and  sand.  To  the 
west  the  soil  becomes  softer,  being  composed  of  clay,  sand, 
and  salt.f 

Within  the  area  of  the  Basin  are  :  the  Timporiogos  or 
Great  Salt,  and  Yutah  Lakes  lying  on  the  east ;  the  Pyra- 
mid, Walker,  and  Carson  Lakes  on  the  west.  The  first  is 
about  70  miles  long,  arid  40  to  60  wide.  The  water  is 
exceeding  salt  and  bitter, — the  chloride  of  sodium  com- 
prising 97.80  parts  in  100.  To  the  south-east  lies  the 
fresh  water  lake,  Yutah,  which  empties  its  waters  into  the 
former.  It  is  20  miles  long  and  6  wide.  Between  these 
lakes  and  the  mountains  in  which  the  Sacramento  rises,  is 
a  vast  valley,  supposed  to  consist  chiefly  of  sandy  plains, 
from  which  no  egress  for  water  has  been  discovered,  the 
rivers  losing  themselves  in  the  sand.  Approaching  the 
mountains  from  Pyramid  Lake,  volcanic  appearances  in- 
crease, the  plains  being  covered  with  scoriae,  and  the 
mountain  ridges  composed  of  black  basaltic  rocks.  Nu- 
merous warm  springs,  impregnated  with  salt,  sulphur,  and 
magnesia,  occur  on  the  flanks.  The  ascent  of  the  Sierra 
Nevada  begins  at  the  lake  ;  reddish  and  brown  sandstone 
are  first  met  with,  then  conglomerates,  granites,  and,  above 
all,  basalt. J 

The  mountain  masses  of  Old  California  extend,  undi- 
vided, to  the  peak  of  San  Bernardino,  where  they  separate 
into  the  two  principal  ranges — the  Sierra  Nevada  and 

*  Wilkes.  f  Bryant.  \  Wilkes. 

976.  Describe  the  Salt  Plain  ?  977.  What  lakes  within  the  Basiu  ? 
978.  What  occur  on  the  east  flanks  of  the  Sierra  I 


T'MTED  STATES,  31  1 

Coast  Range,  which  include  an  extensive  valley.  The 
eastern  chain  runs  nearly  parallel  to  the  coast,  at  the  dis- 
tance of  130  to  150  miles,  and  extends  from  the  42nd  to 
the  35th  degree  of  north  lat.  The  mountains  ascend  gra- 
dually from  the  valley,  and  become  more  and  more  preci- 
pitous, —  rising  like  pyramids  from  a  lofty  plateaux  to  the 
height  of  14,000  or  17,000  feet.  The  collection  of  rugged 
mountains  or  spurs,  which  form  the  Coast  Range,  run  ge- 
nerally parallel  to  the  coast,  rise  to  the  height  of  4,000  feet, 
and  join  the  Shaste  Mountains  towards  their  northern  ter- 
mination. On  the  eastern  side,  this  range  declines  into 
rolling  hills,  while,  on  the  west,  they  present  a  perpendicu- 
lar or  rock-bound  shore,  thus  reversing  the  order  of  the 
Sierra  Nevada.* 

The  section  west  of  the  California  range,  comprising 
re  of  the  territory,  and  to  which  the  world's  attention  is  now 
turned  by  the  discovery  of  its  mineral  riches,  embraces 
three  valleys  —  the  Sacramento,  San  Joachin,  and  San  Juan. 
The  first  extends  from  40°  30'  north  to  the  south  1  80  miles, 
and  is  an  inclined  prairie  of  alluvial,  rising  about  four  feet 
to  the  mile,  and  divided  into  two  distinct  terraces  through- 
out its  length,  called  the  upper  and  low  prairies.  The  low 
undulating  hills  which  form  the  upper  prairie,  project  into 
the  lower  prairie  to  various  distances,  and  gives  its  bound- 
ary an  irregular  outline  ;  the  heig  i!  of  this  upper  prairie 
above  the  lower  is  about  60  feet,  the  slope  varying,  and,  in 
some  instances,  is  very  steep.  The  upper  prairie  is  about 
250  feet  above  the  level  of  the  river,  and  inclines  to  the 
south.  Its  undulating  hills  consist  of  a  clayey  and  sandy 
loam,  gravel,  and  pebbles,  while  the  soil  of  the  lower  prai- 
rie is  rich  alluvial.  The  Bute  Hills  rise  to  the  height  of 
1794  feet  above  the  plain,  the  base  being  nearly  on  a  level 
with  the  upper  prairie.  The  valley  of  San  Joachin  is  140 
miles  long  and  50  wide  ;  its  lower  prairie  is  almost  want- 
ing, yet  it  has  two  distinct  elevations,  the  difference  in  level 

*  Wilkes. 


979.  Describe  the  mountain  ranges?     980      Dp-rril^  the  valley 
of  the  Sacramento!      081.  U'Jiat  it,  taid  of  tin*  tan  JuaUiin  va!le\"? 


312  GEOGRAPHICAL    GEOLOGT. 

averaging  40  feet.  The  valley  is  300  miles  long  and  60 
broad,  being  elevated  only  a  few  hundred  feet  above  the 
level  of  the  sea.  The  surface  along  the  lakes,  arid  river 
consists  of  level  plains,  changing  into  undulating  ground 
nearer  the  foot  hills  of  the  mountains.  Both  lakes  are 
surrounded  by  extensive  sloughs,  the  earth  being  a  rich  al- 
luvial deposite  from  the  surrounding  mountains.  The  val- 
ley of  San  Juan  is  situated  at  the  south  of  San  Francisco 
Bay,  being  60  miles  long,  from  15  to  20  in  width.  It  is 
apparently  a  level  plain,  but  ascends  gradually  towards  the 
south  ;  the  plain  extends  to  the  foot  of  the  high  hills  on 
the  east,  but  on  the  west,  it  has  the  undulating  hills  of  the 
Sacramento  valley,  but  not  their  irregular  outline.* 

A  volcanic  range  on  the  Ocean  side  of  the  Peninsula  runs 
parallel  to  a  similar  and  loftier  series  on  the  continental 
side,  and  the  two,  terminating  northwards  in  an  elevated 
plateau,  gradually  combine  and  culminate  in  the  lofty 
mountain  of  San  Bernardino.  They  again  diverge,  form- 
ing the  two  chains  enclosing  the  aforesaid  valleys.  The 
eastern — the  Sierra  Nevada — carries  on  the  chain  of  high- 
lands as  far  as  Oregon,  and  there  meets  with  another  and 
transverse  group  of  mountains,  extending  from  Cape  Men- 
docino  north  east,  and  culminating  at  Mount  Shaste.  Near 
the  sea,  the  rocks  are  primitive,  arid  probably  porphyries  of 
varied  character,  like  those  in  the  Rocky  Mountains,  and 
also  further  south. 

About  70  miles  north-east  from  the  Bay  of  San  Fran- 
cisco, a  spur  is  given  off  from  the  chain  of  the  Sierra  Ne- 
vada, which  contains  an  active  volcano.  In  the  main  chain 
of  mountains  to  the  south,  porphyries  and  limestones  form 
the  flanks  ol  the  chief  elevations,  and  of  the  whole  central 
ridge ;  these  have  been  elevated  often  to  considerable 
heights,  arid  often  there  appear  rocks  more  distinctly  volca- 
nic, presenting  either  true  cvultes  of  lava  or  trachytic 

*  Ansted. 

982.  Where  is  the  valley  of  the  San  Juan  situated?  983.  What 
is  the  extent  of  the  volcanic  range?  984.  What  is  the  geological 
character  of  the  mountain  chain  to  the  south  ? 


T'MTF.T)  STATES.  313 

rocks,  which,  on  the  plateau,  occupy  vast  tracks  by  the 
side  of  the  porphyries.  Extensive  lacustrine  deposits  re- 
pose on  these,  consisting  of  rounded  flints,  covered  by  marls 
and  handsome  clays.  On  the  Pacific  coast  granite  comes 
more  into  view,  while  further  north  than  Mexico,  trachytic 
rocks,  occasionally  metalliferous,  are  crossed  at  various 
points  by  lava  currents.  As  they  advance  further  north, 
in  the  same  direction,  the  distinctly  volcanic  products  are 
gradually  less  nearly  in  contact,  while  altered  schists,  dior- 
ites,  and  metamorphic  limestones  appears,  and  are  traversed 
by  veins  of  quartz  containing  gold,  and  often  silver.  It 
appears,  also,  that  the  alluvia  derived  from  these  veins  is, 
throughout  the  range,  chiefly  on  the  western  side.  * 

The  Sierra  Nevada  range  is  primary,  granite  fonning  the 
backbone  rock.  The  group  of  porphyritic  formations, 
non-metalliferous,  reposes  on  primary  rocks  ;  the  other, 
often  metalliferous,  rests  on  clay-slate  or  on  talcose  slate 
with  transition  limestone  Entering  the  Shaste  Mount- 
ains, trachytic  rocks  will  be  found  to  be  abundant  ;  but 
talcose  rocks  constitute  the  greater  part  of  the  ridges  along 
the  upper  part  of  the  Sacramento  valley.  The  Shaste 
Peak  is  one  of  the  lofty  volcanos  of  the  Cascade  range. 
Fronting  the  Peak,  the  plain  is  covered  with  hillocks  of  a 
porphyritic  lava  ;  and  to  the  east  of  it,  occurs  a  very  hot 
spring.  Obsidian  is  said  to  exist  in  the  same  region.  The 
granite  of  the  Shaste  region  is  mostly  albitic  ;  and  no  true 
gneiss  is  seen  in  the  mountains.  Compact  hornblendic 
rocks,  which  occur  upon  the  Shaste  river,  and  the  syenites 
pass  into  a  compact  hypersthenic  rock,  which  abounds 
along  Destruction  River  in  the  Shaste  Mountains.  The 
talcose  rocks  of  this  region  are  generally  compact  and  irre- 
gularly fissured  ;  and  it  appears  that  the  jasper  and  prase 
rocks  are  closely  connected  with  the  series.  Serpentine  is 
largely  developed  in  high  ridges  to  the  north-west  of  the 
Shaste  Mountains,  the  general  color  being  a  dark  green. 

*  Ansted. 


985.  Of  what  formation  is  the  Sierra  Nevada?     986.  What  rocks 
abound  iu  the  Shaste  mountains  ? 


3  1  4  GEOGI!  A  P  H  1C  A  L  <  I  F.OLOO  Y 

There  are  also  seams  of  amianthus.  The  rock  is  also 
found  in  the  Shaste  Mountains.  "  The  talcose  forma- 
tions," says  Professor  Dana,  in  his  Geol.  Ex.  Ex.,  "  was 
first  met  with  travelling  south  from  the  Umpqua  ;  next 
\ve  came  upon  syenite,  then  true  granite,  upon  the  Shaste 
River.  After  passing  a  region  of  basalt  and  sandstone,  in 
the  vicinity  of  the  Klamet,  we  crossed  a  prairie,  covered 
in  many  parts  with  pebbles  from  the  talcose  formation ; 
then  the  foot  of  a  ridge  of  serpentine  ;  and  then  entered 
into  a  region  of  syenite  at  the  foot  of  the  Shaste  Mountains. 
For  20  miles  in  the  mountains,  these  rocks  were  interrupt- 
ed by  trachytes.  Boulders  of  talcose  rock  and  syenite  oc- 
curred abundantly  along  the  head  waters  of  the  Sacra- 
mento ;  and  within  a  mile,  granite  boulders  were  inter- 
mingled. A  mile  beyond,  granite  became  the  prevailing 
rock ;  and  at  the  centre  of  the  granite  region,  lofty  pin- 
nacles and  needle  peaks  peered  above  the  forests  around, 
to  a  height  of  3,000  feet.  We  next  passed  successively 
to  hornblende  rocks,  talcose  and  prasoid  rocks,  with  proto- 
gine  and  some  serpentine.  Talcose  rocks  and  slates  were 
again  met  with  near  San  Francisco.  Large  beds  of  con- 
glomerates and  sandstone  were  found  in  the  Shaste  Mount- 
ains. Following  down  Destruction  River,  we  travelled  for 
1 8  miles  before  reaching  the  Sacramento  plains.  The 
slate  appears  to  be  the  lower  member  of  the  series  in  the 
Shaste  Mountains,  and  the  puddingstone  the  upper." 

The  upper  part  of  the  Sacramento  valley  is  100  miles, 
long,  the  lower,  200  The  terrace  is  mostly  about  60  feet 
high;  but  the  upper  plain  gradually  rises  to  150  or  200 
feet.  On  the  plains  nothing  but  mineral  deposits  are  met 
with  until  reaching  the  Sacramento  Bute,  which  is  an  an- 
cient crater,  consisting  of  trachyte  arid  trachytic  porphyry. 
It  will  become  valuable  for  its  stone  quarries.  The  gold 
district  lies  north  of  San  Francisco,  being  a  broad  tract  en- 
closed on  the  east  by  a  lofty  arid  recently  elevated  tract, 
partly  volcanic,  partly  trachytic  but  every  where  exhibit- 
ing igneous  rocks.  The  metal  has  hitherto  been  obtained 

987.  What  does  Dana  say  concerning  the  talcose  formation?  988. 
How  high  is  the  terrace  ?  989.  Describe  the  gold  district  ? 


UNITED  STATES.  31 5 

from  alluvial  sand  and  gravel,  being  mixed  with  and  form- 
ing part  of  quartz  rock  and  pebbles,  occurring  in  the  mud 
and  gravel  which  form  the  present  beds  of  streams,  and 
also  iii  the  former  and  now  dry  beds  of  such  streams.  The 
crevices  of  rocks  also  contain  a  good  supply.* 

The  gravel  of  the  district  is  the  rock  ready  pulverized  by 
natural  causes.  The  streams  washing  over  the  soil,  still 
farther  aid  in  the  preparation,  by  collecting  the  gold  into 
the  bottom  of  the  valleys,  and  carrying  off  the  light  gravel 
and  sand,  thus  leaving  the  grains  of  metal  along  the  beds 
of  the  streams  and  the  bottoms  of  ravines.  The  region 
covered  by  the  debris  of  the  mountains  is  as  wide  as  the 
vast  prairies  of  its  long-reaching  rivers,  and  the  slopes  that 
rise  into  the  ranges  on  either  side.  The  gravel  of  these 
slopes,  and  the  stratified  earth  and  gravel  of  the  plains 
may  therefore  contain  gold  ;  but  the  parts  more  nearly  in 
the  vicinity  of  the  particular  auriferous  rocks,  naturally 
prove  most  productive.  Compact,  slightly  glistening,  slaty 
rocks,  of  various  dark  colors,  the  talcose,  more  or  less 
greasy  in  look  or  feel,  and  often  greenish,  and  chloritic, 
mostly  of  a  darker  olive  green  color,  contain  often  beds  or 
veins  of  quartz  in  which  the  gold  is  found. t  Dikes  or 
beds  of  quartz  rock,  many  feet  in  thickness,  and  often  of 
great  length,  are  numerous,  and  generally  among  nearly 
vertical  strata  of  some  form  of  slate  or  gneiss  rock.  The 
diluvium,  where  the  diggings  have  been  carried  on,  varies 
from  half  a  foot  to  several  feet  in  thickness,  and  rests,  un- 
conformably,  on  a  bed  of  agillite  or  gneiss,  running  about 
north  north-west  and  south  south-east,  and  dipping  nearly 
perpendicularly.  The  clay-slate  presents  a  very  irregular 
surface,  with  abundant  little  pockets  for  retaining  the 
gold,  which  is  found  most  plentifully  on  its  surface  and  in 
its  crevices.  Where  the  gold  is  dug  from  the  ravines,  the 
underlying  rock  is  some  form  of  this  slate ;  and  on  the 
river,  the  gold  stratum  rests  on  a  stratum  of  coarse  granitic 
sand.  The  richest  excavations  have  been  in  the  bottoms 
*  Ansted.  t  Dana. 

990.  What  rocks  prove  most  productive?     991.  Describe  the  di- 
luvium ?     992.  Where  and  how  does  the  gold  occur  f 


316  GEOGRAPHICAL    GEOLOGY. 

of  dry  ravines,  though  gold  is  found  on  the  slopes,  and 
even  on  the  summits  of  hills.* 

The  "dry  diggings,"  which  is  an  upland  marsh,  is  con- 
sidered preferable  to  the  "  wet."  In  the  former,  the  metal 
is  found  in  lumps,  and  in  the  crevices  of  rocks,  and  lies 
from  a  few  inches  to  three  or  four  feet  below  the  surface  : 
In  the  latter,  it  occurs  in  flakes  or  scales.  In  the  streams, 
the  usual  process  of  procuring  it  is  by  throwing  up  dikes 
and  turning  the  water  from  its  channel,  or  drawing  por- 
tions of  the  river's  bed.  In  the  eddies  of  the  main  stream, 
it  can  be  seen  in  great  abundance,  an  at  a  depth  of  25  or 
30  feet  in  many  places. 

Auriferous  districts  and  mountains  are  rarely  limited  to 
small  areas,  and  the  fact  that  no  part  of  the  world  con- 
tains a  greater  mass  of  porphyrines  than  the  cordillera 
renders  probable  the  existence  of  a  considerable  tract  over 
which  similar  repositories  exist.  It  is  reported  that  gold 
occurs  near  Tule  lake,  near  Monterey,  on  the  east  side  of 
the  Sierra  Nevada ;  and  that  a  rich  placer  has  been  dis- 
covered near  the  boundary  line  between  California  and 
Oregon.  The  porphyraceous  chain,  of  which  the  range 
in  California  is  a  part,  extends  almost  in  the  direction  of  a 
meridian,  7500  miles  from  one  hemisphere  to  the  other, 
and  throughout  its  whole  length  appears  highly  metalli- 
ferous ;  but  amidst  many  indications  of  aureate  deposits, 
no  mine  has  yet  been  discovered  which  can  be  compared 
in  richness  to  those  of  the  wide  and  more  than  Pactolian 
plains, 

Where  Sacramento  floats  the  desert  lands, 
And  leaves  a  rich  manure  of  golden  sands. 

But  great  as  are  the  discoveries  of  gold,  they  are  equalled 
by  those  of  mercury.  It  is  found  in  various  places,  even 
within  three  miles  of  San  Francisco.  Forbes'  mine  is  sit- 
uated near  San  Juan,  in  a  spur  of  the  mountains,  1,000 
feet  above  the  level  of  the  bay  of  San  Francisco.  The 

*  Lyman. 

993.  What  is  said  of  auriferous  districts  ?  994.  What  other  me- 
tal* are  found? 


MEXICO. CENTRAL   AMERICA.  317 

cinnabar  occurs  in  a  large  vein  dipping  at  a  strong  angle 
to  the  horizon.  Lead  mines  exist  at  Sonoma.  The  other 
metals  are  platinum,  silver,  copper,  iron,  and  tin.  Sul- 
phur, nitre,  muriate  and  carbonate  of  soda,  and  bitumen, 
abound  ;  bituminous  coal  is  known  to  exist. 

From  official  analyses,  we  learn  that  the  gold  dust  yields 
983  pure  gold  ;  the  melted  metal  yielding  within  6,  1000, 
or  $6  in  the  $1000,  of  the  mint  standard  of  900.  In  the 
assays  of  the  melted  gold,  the  results  showed  a  variation 
in  fineness  from  892  to  897  thousandths  ;  the  average  of 
the  whole  being  894.  The  average  value  per  ounce  of 
the  bullion  assayed,  before  melting,  was  $18. 05.};  that  of 
the  same  in  bars,  after  melting,  $18.50  The  specimens  of 
cinnabar  yielding  nearly  one-third  of  their  weight  in  mer- 
cury. 

MEXICO. — Mexico  consists  mainly  of  a  vast  and  very 
elevated  table-land,  being,  in  fact,  a  flattening  down  of  the 
Andes  on  the  south,  and  the  Rocky  Mountains  on  the 
north.  This  vast  plain,  1,500  miles  over,  is  occasionally 
diversified  by  an  elevated  insulated  peak,  which  is  often  a 
volcano,  recent  or  extinct.  The  basis  of  the  country  seems 
to  be  primary  rocks  ;  such  as  gneiss  and  granite  ;  but  its 
upper  portion  is  covered  with  porphyry  and  trachyte.  Se- 
condary sandstone  and  limestone  also  occur.  A  line  of 
volcanos,  of  which  there  are  five  principal  vents,  traverse 
Mexico  from  east  to  west,  about  in  the  lat.  of  the  capital. 
The  rocks  are  rich  in  silver  and  gold.  They  occur  in  veins 
traversing  clay-slate,  and  talcose  slate,  transition  lime- 
stone, grauwacke,  and  porphyry.  Silver  mines  number 
3,000.  Tin,  copper,  lead,  mercury,  and  iron  abound,  as 
also  beds  of  rock-salt  on  the  Colorado.  The  gold  is 
mixed  with  silver  or  iron,  and  generally  in  the  sulphurets 
of  these  metals.  Oaxaco  contains  the  only  auriferous 
veins  worked  as  gold  mines  in  Mexico. 

CENTRAL  AMERICA. — This  country  is,  for  the  most  part, 
mountainous,  and  abounds  in  volcanos.  Its  geology  is 

995.  State   the   result  of  the   analysis  of  the   gold  dust  ?     996. 
What  rocks  in  Mexico?     997.  What  minerals  does  Mexico  produce? 
998.  What  in  raid  of  Central  America? 
14* 


318  GEOGRAPHICAL    GEOLOGY. 

similar  to  that  of  Mexico,  on  the  north,  and  of  New  G  ra- 
nada,  on  the  south.     Silver  and  sulphur  exist 

WEST  INDIES. — These  islands  are  formed  by  the  Ap- 
palachian chain,  and  many  contain  mountains,  which  in 
Cuba,  Hayti,  and  Jamaica,  are  about  9,000  feet  high. 
The  highest  in  Cuba,  consist  of  mica-slate,  arid  sieriite, 
gneiss,  and  granite,  project  through  the  secondary  forma- 
tions of  the  lower  regions.  Copper,  gold,  and  silver  occur  ; 
and  coal  exists  in  a  vein.  There  is  a  granitic  mountain 
in  the  south  part  of  Hayti.  Grauwacke  with  trap  chiefly 
makes  up  the  highest  part  of  Jamaica.  Over  this  lie  red 
sandstone,  marl,  limestone,  trap,  porphyry,  arid  superficial 
accumulations.  The  eastern  of  the  Caribbee  Isles  are 
mostly  limestone.  Antigua  "  consists  of  grauwacke,  re- 
cent calcareous  dep>*  U\  and  trap.  Lying  above  the  first, 
is  a  silicious  deposit  « ri  bracing  an  immense  number  of 
silicified  trees,  along  with  vast  quantities  of  shells.  These 
form  splendid  agates.  In  St.  Croix  are  grauwacke,  and 
tertiary  and  alluvial  limestone  ;  but  no  uristratified  rocks. 
The  tertiary  is  mostly  indurated  limestone,  abounding  in 
corals  and  shells.  In  the  recent  deposit  on  the  shores 
were  found  human  skeletons.  The  western  parts  of  the 
Caribbee  group  are  chiefly  volcanic  ;  extinct  craters  are 
visible,  and  trachytic  and  basaltic  rocks  are  common. 
Trinidad  is  a  continuation  of  the  continent,  being  mostly 
primary.  Here  is  the  Pitch  Lake,  three  miles  in  circum- 
ference and  of  unknown  thickness." 


SOUTH    AMERICA. 

Every  rock  is  here  developed  on  a  magnificent  scale. 
The  chalk  formation  sometimes  rises  13,000  feet.  Gra- 
nite and  gneiss,  for  the  most  part,  form  the  basis  of 
the  Andes  ;  but  are  covered  by  an  immense  deposit 
of  ancient  volcanic  rocks.  The  elevated  table-lands 

999.  What  rocks  abound  in  the  West  Indian  isles?     1000.  What 
is  said  of  the  geology  of  South- America? 


NEW  GKAXADA. VENEZUELA.  319 

near  the  range  are  covered  in  a  measure  by  fossiliferious 
limestone,  which  occurs  from  9,000  to  14,000  feet  above 
the  sea  ;  and  by  new  red  sandstone,  embracing  copper  and 
gypsum.  The  lower  table-land  is  covered  by  diluvial  de- 
tritus, embracing  gold.  The  mountains  in  the  central 
parts  of  America,  lying  east  of  the  principal  Cordilleras, 
are  in  a  measure  composed  of  various  slates  with  quartz 
rock  and  sandstone  ;  the  central  axis  being  usually  prim- 
ary, and  the  slopes  the  older  secondary.  The  plains  be- 
tween the  diflerent  chains  are  extensively  covered  by 
tertiary  strata.* 

In  NEW  GRANADA,  are  very  fine  copper  mines,  near 
Palma  ;  and  at  Choco,  gold,  platinum,  and  titanium  occur. 
The  whole  of  the  Isthmus  of  Panama,  excepting  the  schis- 
tose channel,  which  crosses  it  in  the  meridian  of  the 
Boqueron,  and  the  granitic  line  between  Pequeni  and  San 
Bias,  is  composed  of  porphyritic  and  hornblendic  rocks, 
which  gradually  pass  from  one  to  the  other,  and  run  in 
large  layers,  more  or  less,  in  a  northerly  direction.  In  the 
Boqueron  and  the  Cascajal,  the  schistose  rocks  are  largely 
developed,  and  the  laminated  structure  of  the  hornblende 
rocks  is  well  denned  ;  there  is  a  great  deficiency  of  lime 
and  silica  in  the  latter.  Though  generally  speaking,  the 
porphyritic  hornblende  is  auriferous,  the  gold  is  very  spar- 
ingly disseminated ;  four  rials  a-day  being  the  maximum 
quantity  obtained,  and  that  by  excessive  labor.  The  gold- 
washings  of  Santa  Rita  are  situated  between  the  rivers 
Clara  and  Grande,  and  are  the  product  of  decomposed 
rocks.  Iron  abounds  occasionally  in  great  quantities  in 
the  state  of  the  peroxyd  and  protoxyd  ;  also  hepatic. f 

In  VENEZUELA,  mountains  skirt  the  northern  shore,  and 
savannas  extend  from  the  base  of  the  chain  to  the  Orinoco. 
All  the  rivers  of  Caraccas  to  10°  north  lat.,  flow  over 
golden  sands. 

The  Colombian  States  also  afibrd  some  diamonds,  and 

*  Hitchcock. 

t  V.  Bogat£  Gazette,  September  9th,  1847. 

1001.  Give  the  geology  of  the  Isthmus  of  Panama  ?     1002.  What 
t*  said  of  Venezuela  ? 


320  GEOGRAPHICAL    GEOLOGY. 

'many  other  precious  stones.  Gold,  silver,  mercury,  cop- 
per, tin,  and  rock-salt,  abound.  The  Pacos  de  Oro  con- 
sists of  ores  of  iron  and  copper  oxides  with  much  gold. 

GUYANA  has  more  of  a  flat  than  mountainous  aspect. 

BRAZIL  is  mountainous  on  the  coast ;  in  the  centre  are 
the  llanos  which  rise  into  lofty  chains  of  mountains.  It  is 
most  celebrated  for  its  gems,  especially  its  diamonds. 
Gold  is  found  on  both  sides  of  the  Brazilian  Andes,  from 
the  5th  to  30th  degree  south  lat.  It  is  found  chiefly  in 
the  affluents  of  the  Francisco.  The  rocks  are  granite  in- 
clining to  gneiss,  with  some  hornblende  arid  often  mica. 
The  gold  mostly  lies  in  cascalhas.  In  Villa  Rica,  Minas 
Geraes,  Cuyaba,  and  Gongo  Soco,-  are  noted  gold  mines. 
Tejuco  is  the  capital  of  the  diamond  district.  Copper 
also  abounds,  and  deposits  of  nitre  and  salt  occur. 

J'ERU,  in  the  western  part,  is  intersected  by  the  Andes 
and  their  Cordilleras ;  the  eastern  part  consists  of  llanos. 
]  iic hiding  BOLIVIA,  it  is  one  of  the  most  remarkable  regions 
on  the  globe  for  the  precious  metals.  The  silver  moun- 
tain of  Potosi  is  eighteen  miles  in  circumference.  Mer- 
cury abounds,  especially  at  Huanca  Velica.  One  mine  is 
70  feet  thick.  The  other  mines  of  gold  and  silver  are 
numerous.  Mines  of  copper,  lead,  tin,  arid  rock-salt  also 
exist.  Most  of  the  mines  are  situated  in  the  eastern  range 
of  the  Andes,  which  consists  of  mica-slate,  sienite,  por- 
phyry, new  red  sandstone,  arid  oolite.*  In  Huailas  and 
Patz,  the  gold  is  mined  in  veins  of  quartz,  variegated  with 
red  ferruginous  spots,  traversing  primary  rocks. 

CHILI  is  enriched  with  valuable  mines  of  gold,  silver, 
copper,  iron,  tin,  and  lead.  Coquimbo  is  rich  in  mines  of 
the  first  three  metals.  Extensive  coal-fields  have  been 
discovered  at  Conception,  and  between  Valparaiso  and 
Santiago. 

The  ARGENTINE  REPUBLIC,  in  the  north  parts,  is  moun- 
tainous ;  the  central  and  south  parts  are  generally  low 

•Hitchcock 

1003.  What  rocks  and  mines  in  Brazil  ?     1004.  What  is  said  of 
Peru  and  Bolivia  ?     1006.  What  metals  <loes  Chili  afford  J 


PATAGONIA-  321 

and  level,  terminating  in  llanos.  The  mountains  yield 
gold  and  silver  ;  and  salt  abounds  in  the  eastern  plains. 

T  he  chief  part  of  PATAGONIA  appears  to  be  a  desert 
region.  Tertiary  stra-ta  with  white  marl  analogous  to 
the  lower  chalk,  and  a  resemblance  to  the  green  sand,  are 
well  developed  on  its  shores.  Coal  has  been  discovered 
at  the  Magellan  Straits. 

The  Smith  American  Islands  are  sterile  regions,  with 
rugged  and  barren  shores. 

[The  history  of  Geology  in  the  United  States  dates  as 
early  as  1807,  when  William  McClure,  a  native  of  Scot- 
land, undertook  a  geological  survey  of  the  United  States, 
prompted  by  a  love  of  science,  and  a  patriotic  devotion  to 
his  adopted  country.  Possessed  of  ample  fortune,  and  an 
indomitable  industry  in  scientific  researches,  he  traversed 
nearly  every  State  in  the  Union,  personally  inspecting  the 
most  remote  districts,  and  enduring  incredible  hardships 
and  privations  in  the  then  unsettled  state  of  much  of  the 
country.  His  pedestrian  excursions  with  his  hammer  in 
his  hand,  and  his  employment  in  breaking  rocks,  the  frag- 
ments of  which  he  examined  so  minutely,  and  preserved 
with  so  much  care  as  valuable  treasure,  led  to  his  being 
often  suspected  and  avoided  by  those  who  witnessed  his 
solitary  avocations,  as  a  lunatic  escaped  from  his  keepers. 
But  he  persevered  in  his  investigations,  devoting  many 
years  of  toil  to  the  work,  and  in  1809  commenced  the  pub- 
lication  of  his  researches  in  the  "Transactions"  of  the 
American  Philosophical  Society,  which  enlisted  the  atten- 
tion of  scientific  men  at  home  and  abroad. 

De  Witt  Clinton,  as  early  as  1814,  urged  upon  the  atten- 
tion of  the  legislature  of  New  York  "  the  importance  of 
employing  men  of  observation  and  science  to  explore  the 
State,  with  a  view  to  its  geology,  mineralogy,  botany,  zoo- 
logy, and  agriculture."  Scientific  associations  in  Pennsyl- 
vania, New  York,  and  Massachusetts,  by  the  publication 
of  their  transactions,  enlightened  the  public  mind  on  the 
importance  of  geology  and  mineralogy,  in  which  they  were 

1006.  What  is  said  of  Patagonia? 


322  CONCLUDING   KEMARKS. 

aided  by  the  circulation  of  Mr.  Featherstonhaugh's  "  Ame- 
rican Monthly  Journal  of  Geology." 

In  1819,  De  Witt  Clinton,  then  Governor  of  New  York, 
again  recom friended  that  the  Board  of  Agriculture,  estab- 
lished by  the  legislature  at  his  instance,  should  be  autho- 
rized to  make  a  statistical  and  geological  survey  of  the 
State,  in  the  hope  that  coal  might  be  found,  and  he  recom- 
mended that  premiums  might  be  offered  for  its  discovery. 

In  1820,  the  late  Stephen  Van  Rensaellaer  employed  at 
his  own  expense,  Drs.  Eaton  and  Beck  to  explore  the  county 
of  Albany,  and  subsequently  Professor  Eaton  extended  his 
survey  under  the  same  patronage  throughout  the  region 
traversed  by  the  Erie  canal,  and  published  his  report  of  the 
strata  from  Boston  to  Buffalo,  in  1824. 

Thus  it  was  that  the  impulse  was  given  to  the  State 
surveys  which  have  since  been  made  with  such  brilliant 
results.  To  North  Carolina  belongs  the  honour  of  having 
first  sent  geologists  in  the  field,  and  Professor  Olmstead's 
report  for  that  State  appeared  in  1825,  since  which  time 
most  of  the  older  States  have  been  explored. 

In  1836,  the  State  of  New  York  authorized  her  survey, 
the  results  of  which  have  been  published  in  successive  vol- 
umes, and  are  honourable  to  the  able  gentlemen  who  have 
completed  it.  And  although  it  has  been  thus  ascertained 
that  coal  is  not  to  be  found  within  the  wide  extent  of  the 
^tate,  as  had  been  confidently  anticipated,  yet  this  destitu- 
tion has  been  compensated  by  the  discovery  of  rich  depo- 
sits of  salt,  lime,  marl,  peat,  and  gypsum,  as  well  as  plum- 
bago, copper,  zinc,  lead  and  iron,  which  have  been  found 
in  numerous  localities,  demonstrating  the  economical  and 
practical  value  of  geology,  as  has  been  done  in  every  in- 
stance in  which  similar  surveys  have  been  made. 

The  importance  of  this  science,  then,  should  inspire  our 
youth  with  an  ardent  desire  for  its  early  acquisition,  apart 
from  the  intrinsic  attractions  of  the  subject  itself.] 


THE  END. 


APPENDIX. 


To  PARAGRAPH  L — Professor  Hitchcock  divides  the  science  into : 
1 .  Economical  Geology,  or  an  account  of  rocks  with  reference  to  their 
pecuniary  value,  or  immediate  application  to  the  wants  of  society ; 
"2.  Sceuographical  Geology,  or  an  account  of  natural  scenery  ;  3.  Scien- 
tific Geology,  or  the  history  of  rocks  in  their  relation  to  science  or 
philosophy. 

To  PARAGRAPH  LXXIIL— Taking  the  specific  gravity  of  lava  at 
2.8,  the  following  table,  made  by  the  same  geologist,  will  show  the 
force  requisite  to  cause  it  to  flow  over  the  tops  of  the  several  vol- 


Name. 

Height  in 

Force  exerted  upon    . 
the  L»v». 

Initial    velo- 
city p'r  Sec'd. 

Stromboli,  (highest  peak,) 
Vesuvius, 
Jorullo, 
Hecla, 
Etna, 
Teneriffe, 
Mouna  Kea, 
Popocatapetl, 
Mount  Elias, 
Cotopaxi; 

2168 

3874 
2942 
6106 
10892 
12464 
14700 
17712 
18079 
18869 

176  Atmospheres, 
314 
319 
413 
882 
1009 
1191 
1435 
1465 
1492 

371  feet. 
496 
602 
570 
832 
896 
966 
1062 
1072 
1104 

Vesuvius  has  launched  scoria  4000  feet  above  its  summit.  Coto- 
paxi has  projected  matter  6000  feet  above  the  summit ;  and  once  it 
threw  a  stone,  of  109  cubic  yards  in  volume,  to  the  distance  of  nine 
miles. 

To  PARAGRAPH  CXIL — We  usually  find  a  fossiferous  formation 
of  any  considerable  thickness  divided  into  many  distinct  beds  of  dif- 
ferent thickness.  At  the  bottom,  perhaps,  will  be  a  layer  of  argil- 
laceous or  siliceous  rock,  with  few  or  no  remains ;  then  will  succeed 
a  layer,  perhaps  calcareous,  full  of  them  in  a  perfect  state ;  next  a 
layer  of  sand  or  clay,  or  limestone  containing  none ;  then  a  laver 
made  up  of  the  fragments  of  rocks,  animals,  and  plants,  more  or  fesu 
comminuted ;  next  a  layer  of  fine  clay  ;  then  a  layer  abounding  in 
remains.  And  thus  shall  we  find  a  succession  of  changes  to  the  top 
of  the  series. — HitcJicork. 


324  APPENDIX. 

The  thickness  in  feet  of  the  fossiliferous  strata  in  Great  Britain  ie 
thus  given  by  Professor  Phillips : 


Tertiary  Strata,  1350 

Chalk,  600 

Green  Sand,  480 

Wealden  Group,  900 

Oolite,  (mean  thickness,)  1 230 

Lias,  1050 

New  Red  Sandstone,  900 


Magnesian  Limestone,  300 

Coal  Measures,  3000 

Millstone  Grit,  900 

Carboniferous  Limestone,  1800 

Old  Red  Sandstone,  9900 

Silurian  Rocks,  7470 

Cambrian  System,  9000 


Professor  Rogers  makes  the  fossiliferous  rocks  in  this  country  be- 
low the  coal  measures  inclusive,  40,000  feet  thick. 

In  the  Andes  and  Himalayas,  rocks,  1 6,000  feet  above  the  sea, 
abound  in  organic  remains.  Gerard  found  ammonites  in  Chinese 
Tartary  at  the  height  of  16,200'feet;  and,  in  Thibet,  he  found  mil- 
lions of  shells  17,000  feet  above  the  sea. 

According  to  Hitchcock,  all  of  two  thirds  of  the  surface  of  our 
existing  continents  are  composed  of  fossiliferous  rocks. 

In  the  Cambrian  and  Silurian  Systems,  Old  Red  Sandstone,  Car- 
boniferous Limestone,  New  Red  Sandstone  Group,  and  Cretaceous 
Group,  all  the  organic  remains  are  of  marine  origin ;  in  Tertiary 
Strata,  they  are  marine  and  fresh  water ;  and  in  the  Oolitic  Group, 
the  marine  predominate.  In  Diluvium,  the  relics  are  terrestrial.  In 
the  Coal  Measures,  the  deposits  are  terrestrial  estuary  ;  in  Wealden 
Rocks,  estuary. 

To  PARAGRAPH  CXIX. — Koferstein  makes  the  whole  number  of 
fossil  species  9620  :  the  number  of 

Mammalia  being  ....     270 

Birds 20 

Reptiles 104 

Fishes .386 

Insects 247 

Spiders,  Crustaceae,  Xyphosura,  Ento-  >      « , . 
mostracea,  Isophoda,  Myriopoda    ( 

Mollusca 6056 

Annelides 214 

Radiata 411 

Polypina 907 

Vegetables  .         .         .         .         .803 

About  half  of  this  number  are  found  above  the  secondary  strata. 

The  older  the  rock,  the  more  unlike  in  general  are  its  organic 
remains  to  existing  species ;  and  the  relics  in  northern  parts  of  the 
globe  correspond  more  nearly  to  existing  tropical  plants  and  animals 
than  to  those  now  living  in  the  same  latitudes.  It  is  probable  that, 
during  the  deposition  of  the  older  fossiliferous  rocks,  the  climate  was 


APPENDIX.  325 

ultia-troptcal  It  is  the  opinion  of  Agaseiz,  that  a  fall  of  tempera- 
ture took  place  near  the  close  of  each  great  geological  period. — 
Hitchcock. 

To  PARAGRAPH  CXX. — According  to  M.  GBppert,  the  numerical 
distribution  of  the  fossil  plants  in  the  various  rocks  is  as  follows : 

Paleozoic.  .  .     52 

Carboniferous  .  .819 

Permian    .  .  .58 

Triassic    .  .  .86 

Oolitic      .  .  .234 

Wealden  .  .  .16 

Cretaceous  -  .  .62 

Tertiary    .  .  .454 

Unknown  .  .11 

1792 

To  PARAGRAPH  CLXXXI. — Agassiz  now  reckons  more  than  1700 
species  of  fossil  fish.  All  the  great  rock  formations,  from  the  grau- 
wacke  upwards,  contain  fishes  ;  but  not  one  species  has  been  found 
that  is  now  living,  or  is  common  to  any  two  of  the  formations. 

To  PARAGRAPH  CCXXII. — Professor  Phillips  now  enumerates  274 
species  of  ammonites,  distributed  as  follows  :  In  grauwacke,  17 ;  car- 
boniferous system,  33;  poikilitio  system,  3; 'oolitic  system,  164; 
cretaceous  system,  57.  Brochant  enumerates  270  species.  It  is 
sometimes  called  cornu  Ammonis. — Vide  Pliny,  37,  10. 

To  PARAGRAPH  CCXLVL— All  the  fossil  relics  of  birds  are  distri- 
buted as  follows :  20  species  in  diluvium  ;  10  in  the  tertiary  strata  ; 
and  one  in  the  Wealden  formation. 

Agassiz  observes,  that  the  tracks  of  birds  may  be  invariably  dis- 
tinguished by  the  number  of  joints  of  the  several  toes;  the  hind  toe 
having  uniformly  two  joints,  the  inner  three,  the  middle  four,  the 
outer  five. 

To  PARAGRAPH  CCXLVIL— With  few  exceptions,  all  fossil  mam- 
malia occur  in  tertiary  strata  and  diluvium.  There  is  reason  to 
believe  that  the  Marsupial  Mammalia  appeared  earlier  on  the  globe 
than  any  other  animals  of  this  class. — Hitchcock. 

To  PARAGRAPH  CCCXII. — Stromboli  appears  to  have  been  in 
ceaseless  activity  for  2000  years.  Kiranea.  and  the  volcano  in  *he 
island  of  Nicaragua,  are  said  to  be  constantly  active.  Many  volcauos 
are  in  a  state  of  moderate  activity,  with  occasional  paroxysms,  until, 
finaily,  a  violent  eruption  gives  vent  to  the  force.  Vesuvius  was 
thus  from  the  commencement  of  the  19th  century  to  October,  1822, 
and  from  1767  to  1779.  In  1805,  '09,  '11,  '12,  and  '19,  ^Etna  was 
eruptive  with  intermediate  agitations,  but  both  these  volcano*  have 
had  periods  of  long  repose.  Popocatepetl  ha.c  been  active  ever  since 
the  conquest  of  Mexico,  and  that  of  Sangay  has  been  in  incessant 


3C6  APPENDIX. 

activity  for  about  a  century.  As  instances  of  remarkable  volcanic 
paroxysms,  there  are  those  of  Vesuvius,  A.D.  79,  203,  472,512,  t-,86, 
993,  1036,  1139,  1306,  1631,  1760,  1794,  and  1822.  ./Etna,  in  1169, 
1329,  1535  ;  this  latter  eruption  lasted  two  years  "  with  terrific  vio- 
lence," and  occurred  after  a  quiescence  of  nearly  100  years.  Tenerifte, 
in  1 704,  1797-8.  San  Georgio,  in  1808.  Palma,  in  1558, 164G,  1777. 
Lanzerote,  in  1730.  Kattlagia  Jokuhl,  in  1 755.  which  lasted  a  year. 
Skaptar  Jokuhl,  in  l7&3.—Silliman. 


INDEX. 


|£7"  The  figures  in  the  columns  beneath  indicate  the  paragraphs  of  the 
text  in  which  the  particular  term  or  subject  is  fully  explained ;  and  the  letter 
n  refers  to  the  notes  accompanying  the  section  in  which  the  paragraph 
occurs. 


PARA. 
Actynolite  ......................    97 

Adipocere  ...................  115,  n 

^  tna,  Viewof  ..................     68 

A  tna,  Eruptions  ol  ..............    73 

Agriculture  aided  by  Geology  •••  331 
Alabaster  ..............    n.  page  254 

Alluvial  ......................     62.  n 

Alluvial  Land  ..........  n.  page  52 

Alps,  Age  of  ................  ----  243 

Alum  ...........................  229 

Amber  ..........................  249 

-Amianthus  ......................  150 

Ammonites  (figured)  ............  222 

Ammonites  Catena  ......  n,  page  179 

A  morphous  .....................     95 

Amygdaloid  ..................  117.  n 

A  nimal  Life,  Effects  of  ........  84-80 

A  nimals.  Classification  of  .......  121 

Anthracite  ..................   192,  n 

Ant:  clinical  Axis  .............  108.  n 

Aqueous  Action  ..............     38.  n 

AQUEOUS  AGENTS  .............    53.  n 

Architecture  aided  by  Geology-  •  332 
Arenaceous  ..............  n.  page  120 

Argillaceous  Compounds  ......  140,  n 

Artesian  Wells  ................  21,  n 

Articulated  Animals  ............  121 

Asaphus  (figured)  ...............  163 

Asbestus  .......................  150 

Asphalte  ........................  289 

Asphalte.  Uses  of  ...............  290 

Asterophy  llites  (figured)  ........  194 

Astraea,  Fossil  (figured  ..........  163 

Astra-a,  Recent  (figured)  ........  300 

ATMOSPHERE,  CONSTITUTION  OF---     33 
Atmosphere,  Pressure  of  .....  33,  n 


Atmosphere,  Utility  of 


34 


PARA. 

ATMOSPHERIC  AGENTS 39.  n 

Atolls,  or  Circular  Coral  Reefs  •  •  304 

Augite 97 

Auiacaria  (fossil) 194 

Auvergne,  Trap  Hills  of 243 

Avalanche n,  page  34 

Avalanches,  Effects  of 43 

BarbadoesTar 289 

Basalt 198,199 

Basin-Form  of  Coal-Fields 201 

Beaches,  Ancient,  or  Raised     78,  264 

Beaches,  Travelling 269 

Beetle  Stones 192 

Beetles.  Fossil 223 

Belemnites 233,  n 

Bellerophon  (figured) 190 

Birds.  Fossil • 246 

Bitumen n.  page  87 

Bitumens. Varieties  of  n,  page  157,  289 
Bitumenization.  Process  of-  •  •  •  115.  n 

Botryoidal 296 

Boulder  Group 252,  * 

Boulders,  where  found 254 

Bovey  Coal 249 

Brine  Springs 213 

BRITISH  DEPOSITS,  TABLE  OF 128 

Burr  Stone  249 


Calamites  (figured) 

Calcareous  Compounds- 

Calc-Sinter • 

Calc-Tuff 

Calymene  (figured)  ••••• 

CannelCoal 191 

Caoutchouc.  Mineral n,  page  157 

Carbonate  of  Lime 97 

€83 


•  •  194 
140,  n 

•  •  2*7 
..  287 

...  183 


328 


INDEX. 


PARA. 

Carbonate  of  Magnesia 97 

Carbonic    Acid   Gas.   Wasting 

Powers  of 50 

Carboniferous  Compounds  ••••  140,  n 

Carboniferous  Limestone 186 

CARBONIFEROUS  SYSTEM 184 

Cartilaginous  Fishes   181 

Catenipora  (figured) 161 

Caverns  in  Limestone  •  •  n,  page  157 

Caverns,  Ossiferous  261 

Cellular  Texture 95 

Central  Heat 21 

Central  Material  of  Globe 14 

Cephalaspis  (figured)  174 

Cestration  of  Australia 224 

CHALK  FORMATION 230,  n 

Chalk  Rock - 231 

Chalybeate  Springs 58 

Chemical  Action 38,  n 

Chemical  Solution 30 

Chloride  of  Sodium 97 

Chlorite 97 

Choke  Damp n,  page  157 

Cidaris  (figured) f.  222 

Clay-Slate  Fossils 160,  161 

CLAY-SLATE  SYSTEM 153 

Cleavage 158,  n 

Clinkstone,  or  Phonolite 198 

COAU  MEASURES •  •  192 

Coal,  Varieties  of 192 

Coal,  Formation  of 1 96,  197 

Coal,  where  found  202 

Coal,  Utility  of- 204 

Coccosteus  (figured) 174 

Cocoa  Nuts  (fossil) 245 

Columnar 95 

Conformable  Strata 108 

Contorted  Strata-  •   107 

Copper,  where  found 169,  213 

Coprolites 191.  n 

Coral.  Uses  of n,  page  254 

Coral  Animalcule  (figured) 300 

CORAL  REEFS 85,  300-306 

Coral  Reefs,  Composition  of 302 

Coral  Reefs,  Formation  of 303 

Coral  Reefs,  Various  Forms  of-  •  •  304 

Coral  Reefs,  Growth  of 306 

Coralloidal 206 

Cornbrash n,  page  179 

Cornish  Clay 139 

Cornstqne  •  • 171 

Crag  Limestone  ....  - 241 

Crater 68,  n 

CRETACEOUS  SYSTEM 230 

Crinoid  Zoophytes 188 

Crust  of  the  Earth 2.  n 

Crust  of  the  Earth,  Causes  Modi- 
fying   •' 4,5 

Crust  of  the  Earth,  Thickness  of    20 
Crust  of  the  Earth,  Mineral  Sub- 
stances Composing 92 


PARA- 

Ctenoid  Fishes 182 

Cuboidal  Structure 95 

Currents,  Oceanic •  •  •  64,  65 

Cyathophyllum, 161 

Cyathophyllum  Basaltiforme 

(figured) 189 

Cycadeae  Fossil 220 

Cycloid  Fishes 189 

Debacle n,  page  231 

Debris 56,  r. 

Degradation 52.  n 

Degrading  Causes 90 

Deinothenum  (figured) 247 

Deltas,  Formation  of 62 

Deltas  of  Principal  Rivers 279-2^1 

Deltoid  Deposits,  Nature  of 277 

Density  of  the  Globe 13,  n 

Denudation  •  • n,  page  44 

Deposits,  Varieties  of n,  page  52 

Devonian  System n.  page  133 

Dialage  Rock 97 

Didelphidae,  Fossil 224 

Diluvium,  Diluvial  Drift 252.  n 

Dip  97 

Dirt- Bed  of  Portland 221 

Dislocation  •••  111,  n 

Disrupting  Masses 110,  n 

Divisional  Planes 186 

Dolerite 313 

Dolomite 205 

Downs,  Formation  of 41 

Downthrow 111,201 

Drainage,  Natural 284 

Dyke Ill,  n 

EARTH,  SURFACE  CONFIGURATION 

OF 23 

Earthquakes  and  their  Effects.    74-76 
Earthquakes,  Examples  of  ......  31C 

Echinidse  (figured) 23S 

Edentata,  Fossil 247 

Edge  Strata  107 

Elaterite,  elastic  mineral  pitch 

n,  page  157 

Electrical  Action 38.  n 

Electricity,  Effects  of 47 

Elementary  Bodies 100 

Elevating  Causes 90 

Elevating  Forces,  Gradual 77 

Embouchure n,  page  231 

Encrinital  Limestone  188 

Encrinite  (figured) 188 

Encrinites,  Varieties  of 18S,  n 

Engineering  aided  by  Geology  •  •  3'3() 

Entrochi n,  page  157 

Eocene n,  page  97.  245 

Erratic  Block  Group 252 

Erratic  Blocks,  where  found  •  ••  •  254 

F,c carpment  10? 

Estuary  Deposits 2>' 


INDEX. 


329 


Euomphalus  (figured) 

Exfoliate 

Exuviae 


PARA. 

..  163 


n,  page  66 

Fault 111.201 

Fauna,  Fossil n,  page  87 

Felspar 97 

Fibrous  Structure  95 

Fire-Clay  204 

Fire-Damp n,  page  157 

Fissile - 95 

Flagstone 172,  180 

Flint,  Uses  of 237 

Flint,  Formation  of- 238 

Flora,  Fossil n,  page  87 

Foliated  Structure 95 

Forests,  Submarine 265 

Forests,  Subterranean 292 

Fossiliferous  Strata n,  page  97 

Fossils,  Nature  of- 112 

Freshets,  or  Land-Floods  n,  page  231 

Friable 95 

Frosts.  Effects  of 42,43,n 

Fuller's  Earth 229 

Ganges.  Delta  of- 281 

Ganoid  Fishes 188 

Garnet, 97. 150 

Gault.  or  Golt,  Clay 231 

Geodes 180,  n 

Geognosy n,  page  17 

Geography,  Physical 6 

Geology,  Definition  of 1,  n 

Geology,  Objects  of 3 

Geology,  Importance  of 327 

GLOBE.  STRUCTURE  AND  CONDI- 
TIONS OF 9 

Globe.  Figure  of 10,11 

Globe,  Density  of- 13 

GLOBE,    CAUSES   MODIFYING 

THE 37,38 

Globe,    Surface,    Configuration 


of 


23 


GXEISS  SYSTEM  ..................  140 

Gneiss,  Composition  of  .......  141-1  43 

Gold,  where  found  .........  169,  204 

Granite  composition  of  ..........  133 

Granite,  where  found  ...........  137 

Granite.  Uses  of  ...............  139 

Granitic  Crust,  or  Basis  .........  131 

Granitic  Rocks  .............  129-133 

Granitic  Districts,  Aspect  of  ----  138 

Granular  Texture  ..............    95 

Graphic  Granite  ................  133 

CTRAUWACKK  SYSTEM  ............  154 

Green  Earth  ....................    97 

Green-sand  Formation  ..........  231 

Greenstone  .....................  198 

Gryphaea  (figured)  ..............  222 

Gypsum  (sulphate  of  liuie)  ----      249 

Gyrgonites  ....................      345 


PARA. 

Hamite n,  page  179 

Harnites  (figured) 233 

Hatchetine.  mineral  tallow  n,  page  157 

Heat,  Central 21 

Heat.  Solar  Effects  of 44,  45 

Heliopora  (figured) 161 

Heterocercal  Fishes 183 

Hitch 111,201 

Holoptychius  (figured) 174 

Horizontal  Strata 107 

Hornblende   97 

Hypogene  Rocks n,  page  101 

Iceberg n,  page  34 

Icebergs,  Effects  of 4a  255 

Ichnites 209,  n 

Ichth)  odorulite 174 

Ichthyolite n.  page  133 

Ichthyosaurus,  Skeleton  of  • 223 

Igneous  Action 38,  n 

IGNEOUS  AGENCIES 66,  67 

Inoceramus  (figured) 190 

Interstratified  Masses 110 

Interstraiificauon.  Pseudo 110 

Iron,  Oxide  and  Sulphuret  of  •  • « •    97 

Ironstone 184 

Ironstone,  Value  of 204 


Jet 

Joints,  or  Backs 
Jungles 


186 
291 


Kaolin 139 

Kupfer-schiefer 213,  n 

Lacustrine  Deposits  283 

Lagoon n,  page  231 

Laminar 95 

LAND  AND  WATER,  DISTRIBUTION 

OF •• 25 

Land  and  Water,  Proportions  of  26,  n 

Lapis  Ollaris 150 

Lava 71,  n;  313 

Lead  Ore 204 

Lepidodendron  (figured)   194 

LIAS  GROUP 217,  n 

Lias  Limestone 229 

Light,  Effects  of 44,45 

Lignite  (wood-coal)   192,  249 

Lithographic  Limestone 213 

Lituite n,  page  179 

London,  Tertiary-Basin 241 

Magnesian  Limestone  206 

Mammillary  Structure 206 

Man  and  his  Works,  found  Fossil, 

286,  295,  324 

Marble 169,  204,  213,  249,  Ac. 

Marine  Silt 267 

Marl.  Varieties  of •  285 

Mastrve  Structure 05 


330 


INDEX. 


PARA. 

Mechanical  Action 33,  n 

Mechanical  Suspension 3 

Megatherium  (figured) 257 

Meiocene n,  page  97,  245 

Metallization,  Process  of  •  •  •  = 117 

Metamorphic  Rocks n,  page  108 

Mica.-.! ••••••    97 

Mca.  Uses  of 139 

MICA  SCHIST  SYSTEM 142 

Millstone  Grit 187 

Mineralogy.  Science  of- 6 

Mineral  Springs 58 

Minerals  the  most  Abundant  •  •  •  •    97 

Mining  aided  by  Geology 329 

Mississippi,  Rafts  of • 62 

Mississippi,  Delta  of 279 

Molluscous  Animals 121 

Monkeys,  Fossil 233 

Moraines 255,  n 

MOUNTAIN  LIMESTONE   186 

Muschelkalk 207 


Naphtha 289,  n 

Neptunian  Rocks n,  page  97 

NEW  RED  SANDSTONE 205,  n 

New  Red  Sandstone,  where  found  211 

Niger,  the  Delta  of  '• 280 

Nile,  Delt; 


taof 


Non-Fossiliferous  Strata  •  -n,  page  97 

Obsidian 313,  n 

Ocean,  Depth  of 26 

OCEAN,  CONSTITUTION  OF 30 

Ocean,  Pressure  of 32,  n 

Ochre 204 

OLD  RED  SANDSTONE  SYSTEM  '  170,  n 
Old  Red  Sandstone,  Fossils  of  173-  175 
Old  Red  Sandstone,  where  found  178 

Olivine 198 

OOLITIC  SYSTEM  216 

Oolitic  System,  where  found 226 

Organic  Action 38.  n 

ORGANIC  AGENTS-   80 

Ornithichnites n,  page  166 

Orthoceratite  (figured) 1 90 

Oryctology 6,  w;  112 

Osseous  Breccia 259,  n 

Osseous  Fishes 1 81 

Ossiferous  Sands  and  Gravels  •  •  •  257 
Ossiferous  Caves  and  Fissures  •  •  260 

Osteolepis  (figured) 174 

Ostrea  (figured) 222 

Outcrop 108 

Outliers 108 

Overlying  Masses 110 

Oxygen,  Wasting  Effects  of 50 

Palaeontology 6,  n 

Palaeotherium  (figured) 247 

Pampas,  Formation  of 284.  n 

Parallel  Road* < 273 


PAfv. 

Paris  Tertiary  Basin '.« 

Peal- Mosses 291-296 

Peat,  Uses  of 290 

Peat,  Varieties  of   29y 

Pecopteris  (figured) 194 

Pecten  (figured) 233 

Permian  System n,  page  165 

Peroxide  of  Iron 167.  n 

Petrifaction,  Process  of    '  ••  •  113,  114 

Petroleum 289 

Pisiform  Iron  Ore  •••- 217 

Pitch,  Mineral 289 

Placoid  Fishes 182 

Plagiostoma  (figured) 233 

Plane  Strata 107 

PLANETARY    RELATIONS   OF   THE 

GLOBE 35 

Plants,  Cellular  and  Vascular  •  ••  120 

Plaster  of  Paris  249 

Plastic  Clay 249 

Pleiocene n,  page  97,  245 

Pleistocene n,  page  97,  245 

Plesiosaurus 


223 

Plutonic  Rocks n,  page  97 

Po.  the  Delta  of  the •••••  279 

Poikilitic  System 205 

Porous 95 

Porphyry n,  page  1:33 

Post-Tertiary 251 

Potstone 150 

Prairies,  Formation  of- 284.  n 

Primary  Districts 149 

Primary  Strata 144 

Primary  Strata,  Origin  of 146 

Primary  Strata,  where  found  •  •  •  •  148 

Primary  Strata,  Uses  of 150 

Producta  (figured)  190 

Protogine 13-3 

Pterichthys  (figured) 174 

Pterodactyle 221 

Puddingstone  172.  n 

Purnicestone 313 

Pyrites n,  page  120 


97 
251 


Quartz 

Quaternary  System 


Radiated  Animals 121 

Rain,  Effects  of 54 

Rai  sed  Beaches 264 

Resins,  Mineral     n,  page  157 

Retepora  (figured) 1 89 

Rhone,  the  Delta  of 279 

Ripple-Mark 176 

Rivers,  Action  of 60,  61 

ROCK  FORMATIONS,  CLASSIFIED 

124-130,  n 

Rock,  Definition  of 125 

Rock-Salt  213 

Rocks,  Stratified,  Aqueous,  or  Se- 
di  memary J>3 


IfCDEX. 


331 


Rocks,  Unstratified,  Igneous,  or 

Volcanic 92,129 

Rocks,  Mechanical  Structure  of-.    9 
Rocks,  Mineral  Composition  of  •  •    96 

Rocks,  Varieties  of- 98 

Rocks,  Chemical  Character  of  •  •  •    99 

Roesione 216 

Roofing-Slate 169 

Rothe-todte-1  iegende 207,  n 

Saccharoid  Texture 95 

Saddle-Back 108 

Saliferous  System 205 

Salt-Rock,  Formation  of 214 

Salt  Springs 213 

Sand-Drift 268 

Sauroid  Animals n,  page  179 

Sauroidichnites n,  page  166 

Savannah,  Formation  of 284,  n 

Scaphite n.  page  179 

Scaphites  (figured)  •  -«« 233 

Schistose 95 

Schorl  n,  page    70 

Scoriae n,  page  59,  313 

Screwstones  (encrinites)  n,  page  156 

Sea,Depthof 28 

Secretion   n,page    66 

Sections,  Natural  and  Artificial 

105,  106 

Sediment- •• 30  ;  n,  page    52 

Selenite  (crystallized  gypsum)  •  •  206 

Septaria 192 

Serpentine 133 

Shell-Beds 298,299 

Shell-Fish,  Effects  of 87 

Shingle-Beaches 269 

Sigilfaria  (figured) 184 

Silicious  Compounds 140,  n 

Silicious  Sinter 288 

Silt n,  page  51;  61,  n 

Silt,  Marine 267 

SiLCRiAS  SYSTEM 155 

Silurian,  why  called  •••-  n,  page  120 
Silurian  System,  Fossils  of  •  •  162,  163 

Silver,  where  found 169,  204 

Slips 111,201 

Snow.  Effects  of 54 

Soil,  Formation  of- 51,308 

Soils,  Varieties  of 309 

Solar  Heat,  Effects  of 44,  45 

Solar  Light,  Effects  of 44,  45 

Sphagnum  Palustre  291 

Sphenopteris  (figured)  194 

Spiritera  (figured) 169 

Springs,  Effects  of 67,  58 

Springs,  Salt 213 

Springs  '    Belles  of 56 

Squamose  95 

St.  Cuthbert's  Beads n.  page  157 

Staffa.  Basa'tic  Columns  of 200 

Stalactite  ai  4  Stalagmite 2W 


MBA. 

Steatite - 07 

Steppes,  Formation  of 284,  n 

Stigmaria  (figured) 194 

Stratification,  Forms  of- 107 

Stratum n,  pagt:    17 

Subcolumnar n,  page  156 

Subcrystalline n,  page  156 

Submarine  Deposits 271 

Subsoils 307 

Sulphate  of  Lime  (gypsum) 97 

Sulphur n,  page  261 

SUPERFICIAL  ACCUMULATIONS 251 

Supraposition  of  Rocks 130 

Surface  Configuration 23,  n 

Syenite 133 

Synclinal  Axis 108,  n 

Syringipora  (figured)  189 


Talc 97 

Talc,  Usesof 139 

Temperature  of  the  Globe-  ••  -16-22,  n 
Temperature  of  the  Earth's  Surface  17 
Temperature  of  the  Earth's  Crust  18 
Temperature  of  Central  Parts  •  •  21 

Terebratula  (figured) 161,  163 

Terraces  in  Valleys 273 

TERTIARY  BASINS 242 

Tertiary  Strata  239 

Tetiapodichnites n,  page  166 

Thames  Tertiary  Basin  (figured)    241 

Theroid  Animals 247,  n 

Tides,  Effects  of 172,180 

Tilestone 180 

Tilted  Up 107 

Tin.  where  found 169 

Toadstone n,  page  133 

Trachyte 313 

Trade-Winds 40 

Transition  Districts,  Features  of  168 
Transition  Districts,  Scenery  of-  -  168 

Transition  Rocks 130,  156 

Transition  Rocks,  Succession  of    159 

Trap  Tuff  198 

Trappean  Rocks 129 

Travertine 287 

Triassic  System n,  page  165 

Trigonia  (figured)   • 222 

Trilobites  (figured) 173 

Tripoli  288 

Trough  Form  of  Coal-Fields  ....  201 

Unconformable  Strata 108 

Upthrow 111,201 

Valley  Deposits 275 

Valleys,  Varieties  of n,  page  231 

Vegetable  Classification 120 

Vegetable  Growth,  Effects  of-  •  81-83 

Veins  Ill 

Vertebrated  Animals 121 

Vesicular  Texture 96 


332 


INDEX. 


PARA 

Vital  Action 38,  n 

Volcanic  Forces,Elevating  powers 

of 73 

Volcanic  Forces,  Effect3  of  70, 311, 312 

Volcanic  Rocks  129 

Volcanoes,  Causes  of-  • 314 

Volcanoes,  Definition  of- 68 

Volcanoes,  Extinct,  Dormant,  and 

Active  311,  n 

Volcanoes,  Products  of- •  313 


PARA 

Water,  Action  of  •••••*« 53,  n 

Waves,  Effects  of 64,65 

WKALDEN  GROUP 217 

Weathering 39,49 

Winds 40,  n 

Winds,  Effects  of 41 

World,  Map  of page    27 


Zechstein 


207, 


INDEX  TO  GEOGRAPHICAL  GEOLOGY. 


PAGE. 

Afghanistan 284 

AFRICA 289 

African  Islands 291 

Arabia 283 

Argentine  Republic 326 

ASIA 281 

Australia 288 

Ballogistan 284 

Barbary 289 

Belgium 299 

Boliva 320 

Brazil 320 

British  America 301 

Central  America 317 

Chili 320 

China 287 

Circassia 282 


.299 


Denmark 297 

Eastern  Africa 291 

England 292 

EUROPE 292 

France 297 

Galicia 299 

Georgia, 282 

Germany 298 

Greece 300 

Greenland 300 

Guyana 320 

Holland 299 

Hungary 299 

India 285 

Ireland 295 

Italy 299 

Japan, 287 


Malaysia 
Mexico 


PAOI 


.319 


New  Granada 319 

NORTH  AMERICA 300 

Norway 296 

Patagroni  a 32 1 

Persia..  ...284 


Peru . 320 

Polynesia 289 

Portugal 298 

Region  of  the  Nile 290 

Russia 296 

Russian  America 300 

Sc  lavonia 299 

Scotland 294 

Sibera 281 

Soudan 291 


SOUTH  AMERICA 318 

South  American  Islands 321 

Southern  Africa 291 

Spain 298 

Sweden 2% 

Swisserland 298 

Tartary 285 

Thibet 285 

Terkey  (in  Asia) 282 

Turkey  (in  Europe) 300 

Transylvania 299 

United  States,  including 

California 302 

Venezuela 319 

Wales...  ...294 


Western  Africa 290 

West  Indies 313 

Zaoara 290 


Davits'  System  of  Mathematics. 


TO   THE   FRIENDS   OF   EDUCATION. 

The  publishers  of  this  series  of  mathematical  works  by  Professor 
CHARLES  DAVIES,  beg  leave  respectfully  to  ask  of  teachers  and  the 
friends  of  education  a  careful  examination  of  these  works.  It  is 
not  their  intention  to  commend,  particularly,  this  Course  of  Math- 
ematics to  public  favor ;  and  especially,  it  is  not  their  design  to 
disparage  other  works  on  the  same  subjects.  They  wish  simply 
to  explain  the  leading  features  of  this  system  of  Text- Books — the 
place  which  each  is  intended  to  fill  in  a  system  of  education — the 
general  connection  of  the  books  with  each  other — and  some  of  the 
advantages  which  result  from  the  study  of  a  uniform  series  of  math- 
ematical works. 

It  may,  perhaps,  not  be  out  of  place,  first,  to  remark,  that  the 
author  of  this  series,  after  graduating  at  the  Military  Academy, 
entered  upon  the  duties  of  a  permanent  instructor  in  that  institution 
in  the  year  1816,  and  was  employed  for  the  twenty  following  years 
in  the  departments  of  scientific  instruction.  At  the  expiration  of 
that  period  he  visited  Europe,  and  had  a  full  opportunity  of  com- 
paring the  systems  of  scientific  instruction,  both  in  France  and 
England,  with  that  which  had  been  previously  adopted  at  the  Mili- 
tary Academy. 

This  series,  combining  all  that  is  most  valuable  in  the  various 
methods  of  European  instruction,  improved  and  matured  by  the 
suggestions  of  more  than  thirty  years'  experience,  now  forms  the 
only  complete  consecutive  course  of  Mathematics.  Its  methods, 
harmonizing  as  the  works  of  one  mind,  carry  the  student  onward 
by  the  same  analogies  and  the  same  laws  of  association,  and  are  cal- 
culated to  impart  a  comprehensive  knowledge  of  the  science,  com- 
bining clearness  in  the  several  branches,  and  unity  and  proportion 
in  the  whole.  Being  the  system  so  long  in  use  at  West  Point,  and 
through  which  so  many  men,  eminent  for  their  scientific  attain- 
ments, have  passed,  it  may  be  justly  regarded  as  our  NATIONAL 
SYSTEM  OF  MATHEMATICS.  Scholars  and  students  who  have  pur- 
sued this  course,  will  everywhere  stand  on  the  highest  level  with 
reference  to  the  estimates  which  themselves  and  others  will  form 
of  this  part  of  their  education. 

The  series  is  divided  into  three  parts,  viz.  :  First — ARITHMETI- 
CAL COURSE  FOR  SCHOOLS.  Second — ACADEMICAL  COURSE.  Third 
— COLLEGIATE  COURSE. 

(3) 


Davies*  System  of  Mathematics. 


The  Arithmetical  Course  for  Schools. 

I.  PRIMARY  TABLE-BOOK. 
II.  FIRST  LESSONS  IN  ARITHMETIC. 
III.  SCHOOL  ARITHMETIC.    (Key  separate/* 


PRIMARY  TABLE-BOOK. 

The  leading  feature  of  the  plan  of  this  work  is  to  teach  the  reading  of  figures 
that  is,  so  to  train  the  mind  that  it  shall,  by  the  aid  of  the  eye  alone,  catch  in- 
stantly the  idea  which  any  combination  of  figures  is  intended  to  express. 

The  method  heretofore  pursued  has  aimed  only  at  presenting  the  combinations 
by  means  of  our  common  language  :  this  method  pioyoses  to  present  them  pure- 
ly through  the  arithmetical  symbols,  so  that  the  pupil  shall  not  be  obliged  to  pause 
at  every  step  and  translate  his  conceptions  into  common  language,  and  then  re- 
translate them  into  the  language  of  arithmetic. 

For  example,  when  he  sees  two  numbers,  as  4  and  8,  to  be  added,  he  shall  not 
pause  and  say,  4  and  8  are  12,  but  shall  be  so  trained  as  to  repeat.  12  at  once,  as  is 
always  done  by  an  experienced  accountant.  So,  if  the  difference  of  these  num- 
bers is  to  be  found,  he  shall  at  once  say  4,  and  not  4  from  8  leaves  4.  If  he  de- 
sires their  product,  he  will  say  32  ;  if  their  quotient,  2  :  and  the  same  in  all  simi- 
lar cases. 

FIRST  LESSONS  IN  ARITHMETIC. 

The  First  Lessons  in  Arithmetic  begin  with  counting,  and  advance  step  by  step 
through  all  the  simple  combinations  of  numbers.  In  order  that  the  pupil  may  be 
impressed  with  the  fact  that  numbers  express  a  collection  of  units,  or  things  of 
the  same  kind,  the  unit,  in  the  beginning,  is  represented  by  a  star,  and  the  child 
should  be  made  to  count  the  stars  in  all  cases  where  they  are  used.  Having  once 
fixed  in  the  mind  a  correct  impression  of  numbers,  it  was  deemed  no  longer 
necessary  to  represent  the  unit  by  a  symbol ;  and  hence  the  use  of  the  star  was 
discontinued.  In  adding  1  to  each  number  from  1  to  10,  we  have  the  first  ten 
combinations  in  arithmetic.  Then  by  adding  2  in  the  same  way,  we  have  the 
second  ten  combinations,  and  so  on.  Each  ten  combinations  is  arranged  in  a 
separate  lesson,  throughout  the  four  ground  rules,  and  each  is  illustrated  either 
by  unit  marks  or  a  simple  example.  Thus  the  four  hundred  elementary  combi- 
nations are  presented,  in  succession,  in  forty  lessons,— a  plan  not  adopted  in  any 
other  elementary  book. 

SCHOOL  ARITHMETIC. 

This  work  begins  with  the  simplest  combination  of  numbers,  and  contains  all 
that  is  supposed  to  be  necessary  for  the  average  grade  of  classes  in  schools.  It 
is  strictly  scientific  and  entirely  practical  in  its  plan.  Each  idea  is  first  presented 
to  the  mind  either  by  an  example  or  an  illustration,  and  then  the  principle,  or 
abstract  idea,  is  stated  in  general  terms.  Great  care  has  been  taken  to  attain 
simplicity  and  accuracy  in  the  definitions  and  rules,  and  at  the  same  time  so  to 
frame  them  as  to  make  them  introductory  to  the  higher  branches  of  mathematical 
science.  No  definition  or  rule  is  given  until  the  mind  of  the  pupil  has  been 
brought  to  it  by  a  series  of  simple  inductions,  so  that  mental  training  may  begin 
with  the  first  intellectual  efforts  in  numbers 

4 


Davies'  System  of  Mathematics. 


The  Academic  Course. 

I.  THE   UNIVERSITY    ARITHMETIC.  (Key separate.) 
II.    PRACTICAL  GEOMETRY    AND  MENSURATION. 

III.  ELEMENTARY    ALGEBRA.  (Key  separate,) 

IV.  ELEMENTARY    GEOMETRY. 

V.    DAVIES'    ELEMENTS   OF  SURVEYING. 


Those  who  are  conversant  with  the  preparation  of  elementary 
text-hooks,  have  experienced  the  difficulty  of  adapting  them  to  the 
wants  which  they  are  intended  to  supply.  The  institutions  of  in- 
struction are  of  all  grades  from  the  college  to  the  district  school, 
and  although  there  is  a  wide  difference  between  the  extremes,  the 
level  in  passing  from  one  grade  to  the  other  is  scarcely  broken. 
Each  of  these  classes  of  seminaries  requires  text-books  adapted  to 
its  own  peculiar  wants  ;  and  if  each  held  its  proper  place  in  its 
own  class,  the  task  of  supplying  suitable  text-books  would  not  be 
so  difficult.  An  indifferent  college  is  generally  inferior,  in  the 
system  and  scope  of  instruction,  to  a  good  academy  or  high-school ; 
while  the  district-school  is  often  found  to  be  superior  to  its  neigh- 
boring academy. 

Although,  therefore,  the  University  Arithmetic  and  the  Practical 
Geometry  and  Mensuration,  have  been  classed  among  the  books 
appropriate  for  academies,  they  may  no  doubt  be  often  advantage- 
ously studied  in  the  common-school ;  so  also  with  the  Algebra  and 
Elementary  Geometry.  The  Practical  Geometry  and  Mensura- 
tion, containing  so  much  practical  matter,  can  hardly  fail  to  be  a 
useful  and  profitable  study. 

DAVIES'  UNIVERSITY  ARITHMETIC. 

The  scholar  in  commencing  this  work,  is  supposed  to  be  familiar  with  the  oper- 
ations in  the  four  ground  rules,  which  are  fully  taught  both  in  the  First  Lessons 
and  in  the  School  Arithmetic.  This  being  premised,  the  language  of  figures, 
which  are  the  representatives  of  numbers,  is  carefully  taught,  and  the  different 
significations  of  which  the  figures  are  susceptible,  depending  on  the  places  in 
which  they  are  written,  are  fully  explained.  It  is  shown,  for  example,  that  the 
simple  numbers  in  which  the  unit  increases  from  right  to  left  according  to  the 
scale  of  tens,  and  the  Denominate  or  Compound  Numbers,  in  which  it  increases 
according  to  a  different  scale;  belong  in  fact  to  the  same  class  of  numbers,  and 
that  both  may  be  treated  under  a  common  set  of  rules.  Hence,  the  rules  for  No- 
tation, Addition,  Subtraction,  Multiplication,  and  Division,  have  been  so  con- 
structed as  to  apply  equally  to  all  numbers.  This  arrangement  is  a  new  one,  and 
is  deemed  an  essential  improvement  in  the  science  of  numbers 

Ifl  developing  the  properties  of  numbers,  from  their  elementary  to  their  highest 
combinations,  great  labor  has  been  bestowed  on  classification  and  arrangement. 
It  has  been  a  leading  object  to  present  the  entire  subject  of  arithmetic  as  forming 


Davies'  System  of  Mathematics. 


a  series  of  dependent  and  connected  propositions ;  so  that  the  pupil,  while  ac- 
quiring useful  and  practical  knowledge,  may  at  the  same  time  be  introduced  to 
those  beautiful  methods  of  exact  reasoning  which  science  alone  can  teach. 

Great  care  has  been  taken  to  demonstrate  fully  all  the  rules,  and  to  explain  the 
reason  of  every  process,  from  the  most  simple  to  the  most  difficult.  The  demon- 
stration of  the  rule  for  the  division  of  fractions,  on  page  147,  is  new  and  consid- 
ered valuable. 

The  properties  of  the  9's,  explained  at  page  93,  and  the  demonstration  of  the 
four  ground  rules  by  means  of  those  properties,  are  new  in  their  present  form, 
and  are  thought  worthy  of  special  attention. 

In  the  preparation  of  the  work,  another  object  has  been  kept  constantly  in 
view  ;  viz.,  to  adapt  it  to  the  business  wants  of  the  country.  For  this  purpose, 
much  pains  have  been  bestowed  in  the  preparation  of  the  articles  on  Weights 
and  Measures,  foreign  and  domestic— on  Banking,  Bank  Discount,  Interest,  Coins 
and  Currency,  Exchanges,  Book-keeping,  &c.  In  short,  it  is  a  full  treatise  on 
the  subject  of  Arithmetic,  combining  the  two  characteristics  of  a  scientific  and 
practical  work. 

Recommendation  from  the  Professors  of  the  Mathematical  Department  of  the 

United  States  Military  Academy 

In  the  distinctness  with  which  the  various  definitions  are  given— the  clear  and 
strictly  mathematical  demonstration  of  the  rules— the  convenient  form  and  well- 
chosen  matter  of  the  tables,  as  well  as  in  the  complete  and  much-desired  appli- 
cation of  all  to  the  business  of  the  country,  the  "  University  Arithmetic"  of 
Prof.  Davies  is  superior  to  any  other  work  of  the  kind  with  which  we  are  ac- 
quainted. These,  with  the  many  other  improvements  introduced  by  the  ad- 
mirable scientific  arrangement  and  treatment  of  the  whole  subject,  and  in  par- 
ticular those  of  the  generalization  of  the  four  ground  rules,  so  as  to  include 
"  simple  and  denominate"  numbers  under  the  same  head,  and  the  very  plain 
demonstration  of  the  rule  for  the  division  of  fractions — both  of  which  are,  to  us, 
original — make  the  work  an  invaluable  one  to  teachers  and  students  who  are  de- 
sirous to  teach  or  study  arithmetic  as  a  science  as  well  as  an  art. 

(Signed,)  D.  H.  MAHAN,  Prof.  Engineering. 

W.  H.  C.  BARTLETT,  Prof.  Nat.  Phil. 
A.  E.  CHURCH,  Prof.  Mathematics. 
United  States  Military  Academy,  Jan.  18,  1847. 

PRACTICAL  GEOMETRY  AND  MENSURATION. 

The  design  of  this  work  is  to  afford  schools  ana  academies  an  Elementary 
Text-Book  of  a  practical  character.  The  introduction  into  our  schools,  within 
the  last  few  years,  of  the  subjects  of  Natural  Philosophy,  Astronomy,  Mineralo- 
gy, Chemistry,  and  Drawing,  has  given  rise  to  a  higher  grade  of  elementary 
studies ;  and  the  extended  application  of  the  mechanic  arts  calls  for  additional 
information  among  practical  rnen.  In  this  work  all  the  truths  of  Geometry  are 
made  accessible  to  the  general  reader,  by  omitting  the  demonstrations  altogether, 
and  relying  for  the  impression  of  each  particular  truth  on  a  pointed  question  arid 
an  illustration  by  a  diagram.  In  this  way  it  is  believed  that  all  the  important 
properties  of  the  geometrical  figures  may  be  learned  in  a  few  weeks ;  and  after 
these  properties  have  been  once  applied,  the  mind  receives  a  conviction  of  their 
truth  little  short  of  what  is  afforded  by  rigorous  demonstration.  The  work  is 
divided  into  seven  books,  and  each  book  is  subdivided  into  sections. 

In  Book  I.,  the  properties  of  the  geometrical  figures  are  explained  bv  questions 
and  illustrations. 


Davies*  System  of  Mathematics. 


In  Book  II.  are  explained  the  construction  and  uses  of  the  various  scales ;  and 
also  the  construction  of  geometrical  figures.  It  is,  as  its  title  imports,  Practical 
Geometry. 

Book  III.  treats  of  Drawing.  Section  I.,  of  the  Elements  of  the  Art ;  Section 
II.,  of  Topographical  Drawing  ;  and  Section  III.,  of  Plan  Drawing. 

Book  IV.  treats  of  Architecture— explaining  the  different  orders,  both  by  de- 
scriptions and  drawings. 

Book  V.  contains  the  application  of  the  principles  of  Geometry  to  the  Mensu- 
ration of  Surfaces  and  Solids.  A  separate  rule  is  given  for  each  case,  and  tho 
whole  is  illustrated  by  numerous  and  appropriate  examples. 

Book  VI.  contains  the  application  of  the  preceding  Books  to  Artificers'  and  Me- 
chanics' work.  It  contains  full  explanations  of  all  the  scales — the  uses  to  which 
they  are  applied — and  specific  rules  for  the  calculations  and  computations  which 
are  necessary  in  practical  operations. 

Book  VII.  is  an  introduction  to  Mechanics.  It  explains  the  nature  and  proper- 
ties of  matter,  the  laws  of  motion  and  equilibrium,  and  the  principles  of  all  the 
simple  machines. 

ELEMENTARY   ALGEBRA. 

This  work  is  intended  to  form  a  connecting  link  between  Arithmetic  and  Alge 
bra,  and  to  unite  and  blend,  as  far  as  possible,  the  reasoning  on  numbers  with  the 
more  abstract  method  of  analysis.  It  is  intended  to  bring  the  subject  of  Algebru 
within  the  range  of  our  common  schools,  by  giving  to  it  a  practical  and  tangible 
form.  It  begins  with  an  introduction,  in  which  the  subject  is  first  treated  men- 
tally, in  order  to  accustom  the  mind  of  the  pupil  to  the  first  processes  ;  after 
which,  the  system  of  instruction  assumes  a  practical  form.  The  definitions  and 
rules  are  as  concise  and  simple  as  they  can  be  made,  and  the  reasonings  are  as 
clear  and  concise  as  the  nature  of  the  subject  will  admit.  The  strictest  scientific 
metiiods  are  always  adopted,  for  the  double  reason,  that  what  is  learned  should 
be  learned  in  the  right  way,  and  because  the  scientific  methods  are  generally  the 
most  simple. 

ELEMENTARY  GEOMETRY. 

This  work  is  designed  for  those  whose  education  extends  beyond  the  acquisi- 
tion of  facts  and  practical  knowledge,  but  who  have  not  the  time  to  go  through 
a  full  course  ofrnathematical  studies.  It  is  intended  to  present  the  striking  and 
important  truths  of  Geometry  in  a  form  more  simple  and  concise  than  is  adopted 
in  Legendre,  and  yet  preserve  the  exactness  of  rigorous  reasoning.  In  this  sys- 
tem, nothing  has  been  omitted  in  the  chain  of  exact  reasoning,  nothing  has  been 
taken  for  granted,  and  nothing  passed  over  without  being  fully  demonstrated 
The  work  also  contains  the  applications  of  Geometry  to  the  Mensuration  of  Sur 
faces  and  Solids. 

SURVEYING. 

In  this  work  it  was  the  intention  of  the  author  to  begin  with  the  very  elemems 
of  the  subject,  and  to  combine  those  elements  in  the  simplest  manner,  so  as  to 
render  the  higher  branches  of  Plane  Surveying  comparatively  easy.  All  the  in- 
struments needed  for  plotting  have  been  carefully  described,  and  the  uses  of  those 
required  for  the  measurement  of  angles  are  fully  explained.  The  Conventional 
Signs  adopted  by  the  Topographical  Bureau,  and  which  are  now  used  by  the  United 
States  Engineers  in  all  their  charts  and  maps,  are  given  in  full.  An  account  is  also 
given  of  the  manner  of  surveying  the  public  lands  ;  and  although  the  method  is  sim- 
ple, it  has  nevertheless  been  productive  of  great  results.  The  work  also  contains 
a  Table  of  Logarithms— a  Table  of  Logarithmic  Sines — a  Traverse  Table,  and  a 
Table  of  Natural  Sines— being  all  the  Tables  necessary  for  Practical  Surveying 

CT1 


Dames'  System  of  Mathematics. 


The  Collegiate  Course. 

I.  DAVIES'  BOURDON'S  ALGEBRA. 
II.  DAVIES'  LEGENDRE'S  GEOMETRY  AND  TRIGONOMETRY. 

III.  DAVIES'  ANALYTICAL  GEOMETRY. 

IV.  DAVIES'  DESCRIPTIVE  GEOMETRY. 

V.  DAVIES'  SHADES,  SHADOWS,  AND  PERSPECTIVE. 
VI.  DAVIES'  DIFFERENTIAL  AND  INTEGRAL  CALCULUS. 


The  works  embraced  under  the  head  of  the  "  Collegiate  Course," 
were  originally  prepared  as  text-books  for  the  use  of  the  Military 
Academy  at  West  Point,  where,  with  a  single  exception,  they  are 
still  used.  Since  their  introduction  into  many  of  the  colleges  of 
the  country,  they  have  been  somewhat  modified,  so  as  to  meet  the 
wants  of  collegiate  instruction.  The  general  plan  on  which  these 
works  are  written,  was  new  at  the  time  of  their  appearance.  Its 
main  feature  was  to  unite  the  logic  of  the  French  School  of 
Mathematics  with  the  practical  methods  of  the  English,  and  the 
two  methods  are  now  harmoniously  blended  in  most  of  our  systems 
of  scientific  instruction. 

The  introduction  of  these  works  into  the  colleges  was  for  a 
long  time  much  retarded,  in  consequence  of  the  great  deficiency  in 
the  courses  of  instruction  in  the  primary  schools  and  academies  : 
and  this  circumstance  induced  Professor  Davies  to  prepare  his 
Elementary  Course. 

The  series  of  works  here  presented,  form  a  full  and  complete 
course  of  mathematical  instruction,  beginning  with  the  first  com- 
binations of  arithmetic,  and  terminating  in  the  higher  applications 
of  the  Differential  Calculus.  Each  part  is  adapted  to  all  the 
others.  The  Definitions  and  Rules  in  the  Arithmetic,  have 
reference  to  those  in  the  Elementary  Algebra,  and  these  to  similar 
ones  in  the  higher  books.  A  pupil,  therefore,  who  begins  this 
course  in  the  primary  school,  passes  into  the  academy,  and  then 
into  the  college,  under  the  very  same  system  of  scientific  in- 
struction. 

The  methods  of  teaching  are  all  the  same,  varied  only  by  the 
nature  and  difficulty  of  the  subject.  He  advances  steadily  from 
one  grade  of  knowledge  to  another,  seeing  as  he  advances  the  con 
nection  and  mutual  relation  of  all  the  parts  :  and  when  he  reacnej 
the  end  of  his  course,  he  finds  indeed,  that  "  science  is  but  know 
ledge  reduced  to  order." 

(8) 


Dames9  System  of  Mathematics. 


DA  VIES'  BOURDON. 

The  Treatise  on  Algebra  by  M.  Bourdon,  is  a  work  of  singular  excellence 
and  merit.  In  France  it  is  one  of  the  leading  text-books.  Shortly  after  its  first 
publication  it  passed  through  several  editions,  and  has  formed  the  basis  of  every 
subsequent  work  on  the  subject  of  Algebra. 

The  original  work  is,  however,  a  full  and  complete  treatise  on  the  subject  of 
Algebra,  the  later  editions  containing  about  eight  hundred  pages  octavo.  The 
time  given  to  the  study  of  Algebra  in  this  country,  even  in  those  seminaries  where 
the  course  of  mathematics  is  the  fullest,  is  too  short  to  accomplish  so  volumin- 
ous a  work,  and  hence  it  has  been  found  necessary  either  to  modify  it,  or  to 
abandon  it  altogether.  The  Algebra  of  M.  Bourdon,  however,  has  been  regarded 
only  as  a  standard  or  model,  and  it  would  perhaps  not  be  just  to  regard  him  as 
responsible  for  the  work  in  its  present  form. 

In  this  work  are  united  the  scientific  discussions  of  the  French  with  the  prac- 
tical methods  of  the  English  school,  so  that  theory  and  practice,  science  and  art, 
may  mutually  aid  and  illustrate  each  other.  A  great  variety  of  examples  have 
also  been  added  in  the  late  editions. 

DAVIES'  LEGENDRE. 

Legendre's  Geometry  has  taken  the  place  of  Euclid,  to  a  great  extent,  both  in 
Europe  and  in  this  country.  In  the  original  work  the  propositions  are  not 
enunciated  in  general  terms,  but  with  reference  to,  and  by  the  aid  of,  the  par- 
ticular diagrams  used  for  the  demonstrations.  It  was  supposed  that  this  de- 
parture from  the  method  of  Euclid  had  been  generally  regretted,  and  among  the 
many  alterations  made  in  the  original  work,  to  adapt  it  to  the  systems  of  in- 
struction in  this  country,  that  of  enunciating  the  propositions  in  general  terms 
should  be  particularly  named ;  and  this  change  has  met  with  universal  acceptance. 

To  the  Geometry  is  appended  a  system  of  Mensuration  of  Planes  and  Solids — 
a  full  treatise  on  Plane  and  Spherical  Trigonometry— and  a  table  of  Logarithms, 
and  Logarithmic  Sines,  Tangents,  and  Secants.  The  whole  forms  a  complete 
system  of  Geometry  with  its  applications  to  Trigonometry  and  Mensuration, 
together  with  the  necessary  tables. 

ANALYTICAL  GEOMETRY. 

This  work  embraces  the  investigation  of  the  properties  of  geometrical  figures 
oy  means  of  analysis.  It  commences  with  the  elementary  principles  of  the  sci- 
ence, discusses  the  Equation  of  the  Straight  Line  and  Circle — the  Properties  of 
the  Conic  Sections— the  Equation  of  the  Plane— the  Positions  of  Lines  in  Space, 
and  the  Properties  of  Surfaces. 

DESCRIPTIVE   GEOMETRY. 

Descriptive  Geometry  is  intimately  connected  with  Architecture  and  Civil 
Engineering,  and  affords  great  facilities  in  all  the  operations  of  Construction. 

As  a  mental  discipline,  the  study  of  it  holds  the  first  place  among  the  various 
branches  of  Mathematics. 

SHADES,  SHADOWS,  AND  PERSPECTIVE. 

This  work  embraces  the  various  applications  of  Descriptive  Geometry  to 
Drawing  and  Linear  Perspective. 

DIFFERENTIAL  AND  INTEGRAL  CALCULUS. 

This  treatise  on  the  Differential  and  Integral  Calculus,  was  intended  to  supply 
the  higher  seminaries  of  learning  with  a  text-book  on  that  branch  of  science.  It 
is  a  work  after  the  French  methods  of  teaching,  and  in  which  the  notation  of  tlu 
French  school  is  adopted. 

(9) 


Parker's  Natural  Philosophy. 


NATURAL    AND    EXPERIMENTAL  PHILOSOPHY 

FOR    SCHOOLS    AND    ACADEMIES, 

BY   R,    G,    PARKER,   A,  M. 

PRINCIPAL  OF  THE  JOHNSON  GRAMMAR  SCHOOL,  BOSTON,  AUTHOR  OF  AIDS 
TO  ENGLISH  COMPOSITION,  ETC.,  ETC. 


I.   PARKER'S  FIRST  LESSONS  IN  NATURAL  PHILOSOPHY. 
II.   PARKER'S  COMPENDIUM  OF  NATURAL  AND  EXPERIMENTAL 
PHILOSOPHY. 


PARKER'S  FIRST  LESSONS  IN  NATURAL  PHILOSOPHY, 

Embracing   the   Elements  of  the    Science.     Illustrated  with   numerous 

engravings.     Designed  for  young  beginners.     Price  38  cts. 

It  is  the  design  of  this  little  book,  to  present  to  the  minds  of  the 
youth  of  the  country  a  view  of  the  laws  of  Nature — as  they  are 
exhibited  in  the  NATURAL  WORLD. 

Reading  books  should  be  used  in  schools  for  the  double  object  of 
teaching  the  child  to  read,  and  storing  his  mind  with  pleasant  and 
useful  ideas. 

The  form  of  instruction  by  dialogue,  being  the  simplest,  has 
been  adopted — and  by  means  of  the  simple  question  and  the  ap- 
propriate answer,  a  general  view  of  the  laws  of  the  physical  uni- 
verse has  been  rendered  so  intelligible,  as  to  be  easily  understood 
by  children  who  are  able  to  read  intelligibly.' 

It  is  confidently  believed  that  this  book  will  form  an  important 
era  in  the  progress  of  common-school  education 

PARKER'S  COMPENDIUM  OF  NATURAL  AND  EXPERIMENTAL 

PHILOSOPHY. 

Embracing  the  Elementary  principles  of  Mechanics,  Hydrostatics,  Hy- 
draulics, Pneumatics,  Acoustics,  Pyronomics,  Optics,  Astronomy, 
Galvanism,  Magnetism,  Electro-Magnetism,  Magneto-Electricity, 
with  a  description  of  the  Steam  and  Locomotive  Engines.  Illustrated 
by  numerous  diagrams.  Price  $1.00. 

The  use  of  school  apparatus  for  illustrating  and  exemplifying 
the  principles  of  Nacural  and  Experimental  Philosophy,  has,  with- 
in the  last  few  years,  become  so  general  as  to  render  necessary  a 
work  which  should  combine,  in  the  same  course  of  instruction,  the 
theory,  with  a  full  description  of  the  apparatus  necessary  for  illus- 
tration and  experiment. 

The  work  of  Professor  Parker,  it  is  confidently  believed,  fully 
rpnets  that  requirement.  "U  is  also  verv  full  in  the  general  facts 

(12) 


Parker's  Natural  Philosophy. 


which  it  presents — clear  and  concise  in  its  style,  and  entirely 
scientific  and  natural  in  its  arrangement.  The  following  features 
will,  it  is  hoped,  commend  the  work  to  public  favor. 

1.  It  is  adapted  to  the  present  state  of  natural  science  ;  embraces 
a  wider  field,  and  contains  a  greater  amount  of  information  on  the 
respective  subjects  of  which  it  treats,  than  any  other  elementary 
treatise  of  its  size. 

2.  It  contains  an  engraving  of  the  Boston  School  set  of  philo- 
sophical apparatus ;  a  description  of  the  instruments,  and  an  ac- 
count of  many  experiments  which  can  be  performed  by  means  ot 
the  apparatus. 

3.  It  is  enriched  by  a  representation  and  a  description  of  the 
Locomotive  and  the  Stationary  Steam  Engines,  in  their  latest  and 
most  approved  forms. 

4.  Besides  embracing  a   copious  account  of  the   principles  ol 
Electricity  and  Magnetism,  its  value  is  enhanced  by  the  introduc- 
tion of  the  science  of  Pyronomics,  together  writh  the  new  science 
of  Electro-Magnetism  and  Magneto-Electricity. 

5.  It  is  peculiarly  adapted  to  the  convenience  of  study  and  of 
recitation,  by  the  figures  and  diagrams  being  first  placed  side  by 
side  with  the  illustrations,  and  then  repeated  on  separate  leaves  at 
the  end  of  the  volume.     The    number  is  also  given,  where  each 
principle  may  be  found,  to  which  allusion   is  made  throughout  the 
volume. 

6.  It  presents  the  most   important   principles  of  science   in  a 
larger  type  ;  while  the  deductions  from  these  principles,  and  the 
illustrations,  are  contained  in  a  smaller  letter.     Much  useful  and 
interesting  matter  is  also  crowded  into  notes  at  the  bottom  of  the 
page.     By  this  arrangement,  the  pupil  can  never  be  at  a  loss  to 
distinguish  the  parts  of  a  lesson  which  are  of  primary  importance  ; 
nor  will  he  be  in  danger  of  mistaking  theory  and  conjecture  for  fact. 

7.  It  contains  a  number  of  original  illustrations,  which  the  author 
has  found  more  intelligible  to  young  students  than  those  which  he 
has  met  elsewhere. 

8.  Nothing  has  been  omitted  which   is  usually  contained  in  an 
elementary  treatise. 

9.  A  full  description  is  given  of  the  Magnetic  Telegraph,  and  the 
principles  of  its  construction  are  fully  explained. 

10.  For  the  purpose  of  aiding  the  teacher  in  conducting  an  ex- 
amination through  an  entire   subject,  or  indeed,  through  the  whole 
book,   if  necessary,  all  the  diagrams  have   been  repeated  at   the 
end  of  the  work,  and  questions  proposed  on  the  left-hand  page  im- 
mediately opposite.     This  arrangement  will  permit  the  pupil  to 
use  the  figure,  in   his  recitation,  if  he  have  not  time  to  make  it  on 
the  hlac.k-board,  and  will  also  enable  him  to  review  several  lessons 
and  recall  all  the  principles  by  simply  reading  the  questions,  and 
analyxing  the  diagrams. 


Parker's  Natural  Philosophy. 


From  the  Wayne  County  Whig. 

After  a  careful  examination  of  this  work,  we  find  that  it  is  well  calculated  for 
the  purpose  for  which  it  is  intended,  and  better  adapted  to  the  state  of  natural 
science  at  the  present  time,  than  any  other  similar  production  with  which  we 
are  acquainted.  The  design  of  the  author,  in  the  preparation  of  this  work,  was 
to  present  to  the  public  an  elementary  treatise  unencumbered  with  matter  that  is 
.not  intimately  connected  with  this  science,  and  to  give  a  greater  amount  of  in- 
formation on  the  respective  subjects  of  which  it  treats,  than  any  other  school- 
book  of  an  elementary  character.  The  most  remarkable  feature  in  the  style  of 
this  work  is  its  extreme  brevity.  In  the  arrangement  of  the  subject  and  the  man- 
ner of  presenting  it,  there  are  some  peculiarities  which  are,  in  our  opinion,  de- 
cided improvements.  The  more  important  principles  of  this  interesting  science 
are  given  in  a  few  words,  and  with  admirable  perspicuity,  in  a  larger  type  ;  while 
the  deductions  from  these  principles,  and  the  illustrations  are  contained  in  a 
smaller  letter.  Much  useful  and  interesting  matter  is  also  given  in  notes  at  the 
bottom  of  the  page. 

This  volume  is  designed  expressly  to  accompany  the  Boston  School  Set  of  Philo- 
sophical Apparatus ;  but  the  numerous  diagrams  with  which  it  is  illustrated,  are 
so  well  executed  and  so  easily  understood,  that  the  assistance  of  the  Apparatus 
is  hardly  necessary  to  a  thorough  knowledge  of  the  science.  The  trustees  of  the 
Lyons  Union  School  having  recently  procured  a  complete  set  of  the  above  Ap- 
paratus, this  work  will  now  be  used  as  a  text-book  in  that  institution. 


LEICESTER  ACADEMY,  April  12,  1848. 
MESSRS.  A.  S.  BARNES  &.  Co.: 

Sirs : — I  have  examined  Parker's  Natural  Philosophy,  and  am  much  pleased 
with  it.  I  think  I  shall  introduce  it  into  the  academy  the  coming  term.  It  seems 
to  me  to  have  hit  a  happy  medium  between  the  too  simple  and  the  too  abstract. 
The  notes  containing  facts,  and  showing  the  reasons  of  many  things  that  are  of 
common  occurrence  in  every-day  life,  seem  to  me  to  be  a  valuable  feature  of  the 
work. 

Very  respectfully,  yours,  B.  A.  SMITH. 


From  the  New  York  Evening  Pojt. 

Professor  Parker's  book  embraces  the  latest  results  of  investigation  on  the  sub- 
'ects  of  which  it  treats.  It  has  a  separate  title  for  the  laws  of  heat,  or  Pyronora- 
ics,  which  have  been  lately  added  to  the  list  ol  sciences,  as  well  as  electro  mag- 
netism and  magneto  electricity.  The  matter  is  well  arranged,  and  the  style  of 
statement  clear  and  concise.  The  figures  and  diagrams  are  placed  side  by  side 
with  the  text  they  illustrate,  which  is  greatly  for  the  convenience  of  the  student. 
We  cheerfully  commend  the  book  to  the  favorable  attention  of  the  public. 


From  the  Albany  Spectator. 

'I  his  is  a  school-book  of  no  mean  pretensions  and  of  no  ordinary  value.  It  is 
admirably  adapted  to  the  present  state  of  natural  science  ;  and  besides  contain- 
ing engravings  of  the  Boston  school  set  of  philosophical  apparatus,  embodies 
more  information  on  every  subject  on  which  it  treats  than  any  other  elementary 
w-jrk  of  its  size  that  we  have  examined.  It  abounds  with  all  the  necessary  helps 
:u  prosecuting  the  study  of  the  science,  and  as  its  value  becomes  known  it  can- 
not fail  to  be  generally  adopted  as  a  text-book. 

14 


Parker's  Natural  Philosophy. 


From  the  Newark  Daily  Advertiser. 

A  work  adapted  to  the  present  state  of  natural  science  is  greatly  needed  in  all 
our  schools,  and  the  appearance  of  one  meeting  all  ordinary  wants  must  be  hailed 
with  pleasure  by  those  who  feel  an  interest  in  the  cause  of  education.  Mr.  Par- 
ker's work  embraces  a  wider  field,  and  contains  a  greater  amount  of  information 
on  the  respective  subjects  of  which  it  treats,  than  any  other  elementary  treatise 
of  its  size,  and  is  rendered  peculiarly  valuable  by  the  introduction  of  the  science  of 
Pyronomics,  together  with  the  new  sciences  of  Electro- Magnetism  and  Magneto 
Electricity.  We  have  seldom  met  with  a  work  so  well  adapted  to  the  conveni- 
ence of  study  and  recitation,  and  regard  as  highly  worthy  of  commendation  the 
care  which  the  author  has  taken  to  prevent  the  pupil  from  mistaking  theory  and 
conjecture  for  fact.  We  predict  for  this  valuable  and  beautifully  printed  w 
the  utmost  success. 

From  the  New  York  Courier  and  Enquirer 

"  A  School  Compendium  of  Natural  and  Experimental  Philosophy,"  by  Richard 
Green  Parker,  has  just  been  issued  by  Barnes  &  Co.  Mr.  Parker  has  had  a  good 
deal  of  experience  in  the  business  of  practical  instruction,  and  is,  also,  the  author 
of  works  which  have  been  widely  adopted  in  schools.  The  present  volume  strikes 
us  as  having  very  marked  merit,  and  we  cannot  doubt  it  will  be  well  received. 

NEW  YORK,  May,  1848. 
MESSRS.  A.  S.  BARNES  &  Co.: 

Gent.  .—I  have  no  hesitation  in  saying  that  Parker's  Natural  Philosophy  is  the 
most  valuable  elementary  work  I  have  seen  :  the  arrangement  of  the  subjects 
and  the  clearness  of  the  definitions  render  it  an  excellent  adjunct  to  a  teacher. 
For  the  last  seven  years  I  have  used  it  in  various  schools  as  a  text-book  for  my 
lectures  on  Natural  Philosophy,  and  am  happy  to  find  that  in  the  new  edition 
much  important  matter  is  added,  more  especially  on  the  subjects  of  Electricity 
and  Electro-Magnetism. 

With  respect,  Gentlemen. 

Your  obedient  servant, 

GILBERT  LANGDON  HUME, 
Teacher  of  Natural  Philosophy  and  Mathematics  in  N.  Y.  city. 

NEW  YORK,  May  2,  I84a 

We  have  used  Parker's  Compend  of  Natural  Philosophy  for  many  years,  and 
consider  it  an  excellent  work  on  the  various  topics  of  which  it  treats. 

Yours,  &LC.  FORREST  &  McELLIGOTT, 

Principals  of  the  Collegiate  School. 

From  the  Lynchburg  Virginian. 

The  volume  before  us  strikes  us  as  containing  more  to  recommend  it  than  any 
one  of  its  class  with  which  we  are  acquainted.  It  is  adapted  to  the  present  state 
of  natural  science  ;  embraces  a  wider  field,  and  contains  a  greater  amount  of  in- 
formation on  the  respective  subjects  of  which  it  treats,  than  any  other  elementary 
treatise  of  its  size.  It  contains  descriptions  of  the  steam-engine,  stationary  and 
locomotive,  and  of  the  magnetic  telegraph.  It  embraces  a  copious  account  of 
the  principles  of  electricity  and  magnetism,  under  all  their  modifications,  and  is 
embellished  by  a  vast  number  of  illustrations  and  diagrams.  There  is  appended 
a  series  of  questions  for  examination,  copious  and  pertinent 

15 


Gillespie's  Manual  of  Road-Making. 


ROADS    AND    RAILROADS. 

A  MANUAL  OF  ROAD-MAKING: 

Comprising  the  principles  and  practice  of  the  Location,  Construc- 
tion, and  Improvement  of  ROADS,  (common,  macadam,  paved 
plank,  &c.,)  and  RAILROADS.  By  W.  M.  GILLESPIE,  A.  M., 
Professor  of  Civil  Engineering  in  Union  College.  Price  $1.50. 

Recommendation  from  Professor  Mahan. 

I  have  very  carefully  looked  over  Professor  Gillespie's  IVlanual  of  Road- 
Making.  It  is,  in  all  respects,  the  best  work  on  this  subject  with  which  I  am  ac- 
quainted ;  being,  from  its  arrangement,  comprehensiveness  and  clearness,  equally 
adapted  to  the  wants  of  Students  of  Civil  Engineering,  and  the  purposes  of  per- 
sons in  any  way  engaged  in  the  construction  or  supervision  of  roads.  The  ap- 
pearance of  such  a  work,  twenty  years  earlier,  would  have  been  a  truly  national 
benefit,  and  it  is  to  be  hoped  that  its  introduction  into  our  seminaries  may  be  so 
general  as  to  make  a  knowledge  of  the  principles  and  practice  of  this  branch  of 
engineering,  as  popular  as  is  its  importance  to  all  classes  of  the  community. 
(Signed,) 

D.  H.  MAHAN, 

Professor  of  Civil  Engineering  in  the  Military  ) 
Academy  of  the  United  States.      \ 

From  a  Report  of  a  Committee  of  the  American  Institute. 

This  work  contains  in  a  condensed  form,  all  the  principles,  both  ancient  and 
modern,  of  this  most  important  art ;  and  almost  every  thing  useful  in  the  great 

mass  of  writers  on  this  subject Such  a  work  as  this  performs  a  great 

service  for  those  who  are  destined  to  construct  roads— by  showing  not  only  what 
ought  to  be  done,  but  what  ought  not  to  be  done  ;  thus  saving  immense  outlay  of 
money,  and  loss  of  time  in  experiments The  committee  therefore,  recom- 
mend it  to  the  public. 

From  the  American  Railroad  Journal. 

The  views  of  the  author  are  sound  and  practical,  and  should  be  read  by  the 
people  throughout  the  entire  length  and  breadth  of  the  land.  .  .  .  We  recom- 
mend this  Manual  to  the  perusal  of  every  tax-payer  for  road-making,  and  to  the 
young  men  of  the  country,  as  they  will  find  useful  information  in  relation  to  each 
department  of  road-making,  which  will  surely  be  useful  to  them  in  after-life. 

From  Silliman's  American  Journal  of  Science. 

If  the  well-established  principles  of  Road-Making,  which  are  so  plainly  set 
forth  in  Prof.  Gillespie's  valuable  work,  and  so  well  illustrated,  could  be  once 
put  into  general  use  in  this  country,  every  traveller  would  bear  testimony  to  the 
fact  that  the  author  is  a  great  public  benefactor. 

From  the  Journal  of  the  Franklin  Institute. 

This  small  volume  contains  much  valuable  matter,  derived  from  the  best 
authorities,  and  set  forth  in  a  clear  and  simple  style.  For  the  want  of  informa- 
tion which  is  contained  in  this  Manual,  serious  mistakes  are  frequently  made, 
and  roads  are  badly  located  and  badly  constructed  by  persons  ignorant  of  the  true 

(16) 


GiUcspie's  Manual  of  Road-Making. 


principles  which  ought  to  govern  in  such  cases.  By  the  extensive  circulation  of 
such  books  as  that  now  before  us,  and  the  imparting  of  sound  views  on  the  sub- 
ject to  the  students  of  our  collegiate  institutions,  we  may  hope  for  a  change  for 
.he  better  in  this  respect. 

From  the  Albany  Cultivator. 

The  author  of  this  work  has  supplied  a  desideratum  which  has  long  existed. 
Perhaps  there  is  no  subject  on  which  information  is  more  needed  by  the  country 
in  general  than  that  of  Road-Making.  Prof.  Gillespie  has  taken  up  the  subject 
in  a  proper  manner,  beginning  the  work  at  the  right  place,  and  prosecuting  it  in 
systematic  order  to*  its  completion. 

From  the  New  York  Tribune. 

It  would  astonish  many  "  path-masters"  to  see  how  much  they  don't  know 
with  regard  to  the  very  business  they  have  considered  themselves  such  adepts  in. 
Yet  all  is  so  simple,  so  lucid,  so  straight  forward,  so  manif^tly  true,  that  the 
most  ordinary  and  least  instructed  mind  cannot  fail  to  profit  by  it.  We  trust  this 
useful  and  excellent  volume  may  find  its  way  into  every  village  library  if  not 
into  every  school  library,  as  well  as  into  the  hands  of  every  man  interested  in 
road-making.  Its  illustrations  are  very  plain  and  valuable,  and  we  cannot  doubt 
that  the  work  will  be  a  welcome  visiter  in  many  a  neighborhood,  and  that  bad 
roads  will  vanish  before  it. 

From  the  Newark  Daily  Advertiser. 

This  elaborate  and  admirable  work  combines  in  a  systematic  and  symmetrical 
form  the  results  of  an  engineering  experience  in  all  parts  of  the  Union,  and  of  an 
examination  of  the  great  roads  of  Europe,  with  a  careful  digestion  of  all  acces- 
sible authorities.  The  six  chapters  into  which  it  is  divided  comprehend  a 
methodical  treatise  upon  every  part  of  the  whole  subject ;  showing  what  roads 
ought  to  be  in  the  vital  points  of  direction,  slopes,  shape,  surface,  and  cost,  and 
giving  methods  of  performing  all  the  necessary  measurements  of  distances,  di- 
rections, and  heights,  without  the  use  of  any  instruments  but  such  as  any 
mechanic  can  make,  and  any  farmer  use.  Bridges,  Railroads,  and  City  Streets 
are  also  treated  of  at  length  and  with  good  sense. 

From  the  Vermont  Chronicle. 

To  selectmen  and  others  who  may  have  any  thing  to  do  with  these  improve- 
ments, we  would  earnestly  recommend  the  book  named  above.  The  author  is  a 
man  of  science,  (Professor  of  Civil  Engineering  at  Union  College,)  and  his  work 
embraces  a  full  discussion  of  both  the  principles  anrf  practice  of  Road-Making 
A  little  study  of  this  work  may  often  lead  to  results  of  importance  to  whole  towns 
and  counties. 

From  the  Home  Journal. 

The  author  of  this  book  holds  a  quill  so  skilful  and  dairtv  in  light  literature, 
that  we  were  not  prepared  with  laurels  to  crown  him  for  a  scientific  work  ;  but 
we  see,  by  the  learned  critics,  that  this  fruit  of  his  study  of  his  profession  as  an 
engineer,  is  very  worthy  of  high  commendation,  and  a  valuable  addition  to  the 
useful  literature  of  the  day. 

(17) 


Willard's  Series  of  School  Histories  and  Charts. 

MRS.  EMMA  WILLARD'S 
SERIES   OP  SCHOOL  HISTORIES  AND   CHARTS, 

1.  WILLARD'S    HISTORY    OF    THE    UNITED    STATES,    OR    RE- 
PUBLIC OF  AMERICA,  8vo.     Price  91. 50. 

II.  WILLARD'S  SCHOOL  HISTORY  OF  THE  UNITED  STATES. 
III.   WILLARD'S    AMERICAN   CHRONOGRAPHER,     $1.00. 
A  CHART  OP  AMERICAN  HISTORY. 


I.  WILLARD'S  UNIVERSAL  HISTORY  IN  PERSPECTIVE. 
II.  WILLrtRD'S  TEMPLE  OF  TIME,     fl.25. 
A  CHART  OF  UNIVERSAL  HISTORY 


W  I  L  L  A  R  D'S 
HISTORY    OF    THE    UNITED    STATES. 


The  large  work  is  designed  as  a  Text-Book  for  Academies  and 
Female  Seminaries :  and  also  for  District  School  and  Family 
Libraries.  The  small  work  being  an  Abridgment  of  the  same,  is 
designed  as  a  Text-Book  for  Common  Schools.  The  originality 
of  the  plan  consists  in  dividing  the  time  into  periods,  of  which 
the  beginnings  and  terminations  are  marked  by  important  events  ; 
and  constructing  a  series  of  maps  illustrating  the  progress  of  the 
settlement  of  the  country,  and  the  regular  advances  of  civilization. 
The  Chronographic  Chart,  gives  by  simple  inspection,  a  view  of 
the  divisions  of  the  work,  and  the  events  which  mark  the  be- 
ginning and  termination  of  each  period  into  which  it  is  divided. 
A  full  chronological  table  will  be  found,  in  which  all  the  events  ot 
the  History  are  arranged  in  the  order  of  time.  There  is  appended 
to  the  work  the  Constitution  of  the  United  States,  and  a  series  ot 
questions  adapted  to  each  chapter,  so  that  the  work  may  be  used 
in  schools  and  for  private  instruction. 

The  Hon.  Daniel  Webster  says,  of  an  early  edition  of  the  above  work,  in  a  letter 
to  th«  author,  "  7  keep  it  near  me,  as  a  Book  of  Reference,  accurate  in  facts  and  dates." 

(18) 


WillanVs  Series  of  School  Histories  and  Charts. 

W  I  LL  ARD'S 
AMERICAN    CHRONOGRAPH  ER, 

DESIGNED    TO    ACCOMPANY    WILLARD's    HISTORY    OF 
THE    UNITED    STATES. 


To  measure  time  by  space  is  universal  among  civilized  nations  -, 
and  as  the  hours,  and  minutes,  and  seconds  of  a  clock  measure  th& 
time  of  a  day,  so  do  the  centuries,  tens,  and  single  years  of  this 
Chronographer,  measure  the  time  of  American  History.  A 
general  knowledge  of  chronology  is  as  indispensable  to  history,  as 
a  general  knowledge  of  latitude  and  longitude  is  to  geography. 
But  to  learn  single  dates,  apart  from  a  general  plan  of  chronology 
addressed  to  the  eye,  is  as  useless  as  to  learn  latitudes  and  longi- 
tudes without  reference  to  a  map.  The  eye  is  the  only  medium 
of  permanent  impression.  The  essential  point  in  a  date,  is  to 
know  the  relative  place  of  an  event,  or  how  it  stands  in  time  com- 
pared with  other  important  events.  The  scholar  in  the  school- 
loom,  or  the  gentleman  in  his  study,  wants  such  a  visible  plan  of 
time  for  the  study  of  history,  the  same  as  he  wants  the  visible 
plan  of  space,  viz.,  a  map  for  the  study  of  geography,  or  of  books 
of  travels.  Such  is  the  object  of  Willard's  Chronographer  oj 
American  History. 

Extract  from  a  Report  of  the  Ward  School  Teachers1  Association 
of  the  City  of  New  York. 

The  Committee  on  Books  of  the  Ward  School  Association  respectfully  report : 

That  they  have  examined  Mrs.  Willard's  History  of  the  United  States  with 
peculiar  interest,  and  are  free  to  say,  that  it  is  in  their  opinion  decidedly  the  best 
treatise  on  this  interesting  subject  that  they  have  seen.  *  * 

As  a  school-book,  its  proper  place  is  among  the  first.  The  language  is  remark- 
able for  simplicity,  perspicuity,  and  neatness ;  youth  could  not  be  trained  to  a 
better  taste  for  language  than  this  is  calculated  to  impart.  The  history  is  so 
written  as  to  lead  to  geographical  examinations,  and  impresses  by  practice  the 
habit  to  read-  history  with  maps.  It  places  at  once,  in  the  hands  of  American 
youth,  the  history  of  their  country  from  the  day  of  its  discovery  to  tne  present 
time,  and  exhibits  a  clear  arrangement  of  all  the  great  and  good  deeds  of  their 
ancestors,  of  which  they  now  enjoy  the  benefits,  and  inherit  the  renown.  The 
struggles,  sufferings,  firmness,  and  piety  of  the  first  settlers  are  delineated  with  a 
masterly  hand. 

The  gradual  enlargement  of  our  dominions,  and  the  development  of  our  na- 
tional energies,  are  traced  with  a  minute  accuracy,  which  the  general  plan  of  the 
work  indicates. 

The  events  and  achievements  of  the  Revolution  and  of  the  last  war,  are 
brought  out  in  a  clear  light,  and  the  subsequent  history  of  our  national  policy 
and  advancement  strikingly  portrayed,  without  being  disfigured  by  that  tinge 

' 


Willard's  Series  of  School  Histories  and  Charts. 

ol  party  bias  which  is  so  difficult  to  be  guarded  against  by  historians  of  their  own 
times. 

The  details  of  the  discovery  of  this  continent  by  Columbus,  and  of  the  early 
settlements  by  the  Spaniards,  Portuguese,  and  other  European  nations,  are  all  ol 
essential  interest  to  the  student  of  American  history,  and  Will  be  found  sufficiently 
minute  to  render  the  history  of  the  continent  full  and  complete.  The  different 
periods  of  time,  together  with  the  particular  dates,  are  distinctly  set  forth  with 
statistical  notes  on  the  margin  of  each  page,— and  these  afford  much  information 
without  perusing  the  pages. 

The  maps  are  beautifully  executed,  with  the  locality  of  places  where  particular 
events  occurred,  and  the  surrounding  country  particularly  delineated.  These 
are  admirably  calculated  to  make  lasting  impressions  on  the  mind. 

The  day  has  now  arrived  when  every  child  should  be  acquainted  with  the  his- 
tory of  his  country ;  and  your  Committee  rejoice  that  a  work  so  full  and  clear  can 
be  placed  within  the  reach  of  every  one. 

The  student  will  learn,  by  reading  a  few  pages,  how  much  reason  he  has  to  be 
proud  of  his  country— of  its  institutions — of  its  founders — of  its  heroes  and  states- 
men :  and  by  such  lessons  are  we  not  to  hope  that  those  who  come  after  us  will 
be  instructed  in  their  duties  as  citizens,  and  their  obligations  as  patriots  7 

Your  Committee  are  anxious  to  see  this  work  extensively  used  in  all  the  schools 
in  the  United  States. 

(Signed,) 

SENECA  DURAND, 
EDWARD  McELROY, 
JOHN  WALSH. 

The  Committee  would  respectfully  offer  the  following  resolution  : 
Resolved,  That  Mrs.  Emma  Willard's  History  of  the  United  States  be  adopted 
by  this  Association,  and  its  introduction   into  our  schools  earnestly  recom- 
mended. 

At  a  meeting  of  the  Board  of  the  Ward  School  Teacners'  Association,  January 
20th,  1847,  the  above  Resolution  was  adopted.— (Copied  from  the  Minutes.) 


From  the  Boston  Traveller. 

We  consider  the  work  a  remarkable  one,  in  that  it  forms  the  best  book  for 
general  reading  and  reference  published,  and  at  the  same  time  has  no  equal,  in 
our  opinion,  as  a  text-book.  On  this  latter  point,  the  profession  which  its  author 
has  so  long  followed  with  such  signal  success,  rendered  her  peculiarly  a  fitting 
person  to  prepare  a  text- book.  None  but  a  practical  teacher  is  capable  of  pre- 
paring a  good  school-book ;  and  as  woman  has  so  much  to  do  in  forming  our 
early  character,  why  should  her  influence  cease  at  the  fireside — why  not  en- 
courage her  to  exert  her  talents  still,  in  preparing  school  and  other  books  foi 
after  years  ?  No  hand  can  do  it  better. 

The  typography  of  this  work  is  altogether  in  good  taste. 

From  the  Cincinnati  Gazette. 

Mns.  WILLARD'S  SCHOOL  HISTORY  OF  THE  UNITED  STATES. — It  is  one  of  those 
rare  things,  a  good  school-book  ;  infinitely  better  than  any  of  the  United  States 
Histories  fitted  for  schools,  which  we  have  at  present.  It  is  quite  full  enough, 
and  yet  condensed  with  great  care  and  skill.  The  style  is  clear  and  simple- 
Mrs.  Willard  having  avoided  those  immense  Johnsonian  words  which  Grirnshaw 
and  other  writers  for  children  love  to  put  into  their  works,  while,  at  the  same 
time  there  is  nothing  of  the  pap  style  about  it.  The  arrangement  is  excellent, 

(20) 


Willard1  s  Series  of  School  Histories  and  Charts. 

the  chapters  of  a  good  length  ;  every  page  is  dated,  and  a  marginal  index  makes 
reference  easy.  But  the  best  feature  in  the  work  is  its  series  of  maps  ;  we  have 
the  country  as  it  was  when  filled  with  Indians ;  as  granted  to  Gilbert ;  as  di- 
vided at  the  time  the  Pilgrims  came  over ;  as  apportioned  in  1643 ;  the  West 
while  in  possession  of  France  ;  the  Atlantic  coast  in  1733 ;  in  1763 ;  as  in  the 
Revolution,  with  the  position  of  the  army  at  various  points  ;  at  the  close  of  the 
Revolutionary  War;  during  the  war  of  1812-15;  and  in  1840:  making  eleven 
most  excellent  maps,  such  as  every  school  history  should  have.  When  we 
think  of  the  unintelligible,  incomplete,  badly  written,  badly  arranged,  worthless 
work  of  Grimshaw  which  has  been  so  long  used  in  our  schools,  we  feel  that 
every  scholar  and  teacher  owes  a  debt  of  gratitude  to  Mrs.  Willard.  Miss 
Robins  has  done  for  English  History,  what  Mrs.  Willard  has  now  done  for 
American,  and  we  trust  these  two  works  will  be  followed  by  others  of  as  high  or 
higher  character.  We  recommend  Mrs.  Willard's  work  as  better  than  any  vre 
know  of  on  the  same  subject ;  not  excepting  Bancroft's  abridgment.  This  work, 
followed  by  the  careful  reading  of  Mr.  Bancroft's  full  work,  is  all  that  would  be 
needed  up  to  the  point  where  Bancroft  stops  ;  from  that  point,  Pitkin  and  Mar- 
shall imperfectly  supply  the  place,  which  Bancroft  and  Sparks  will  soon  fill. 

From  the  United  States  Gazette. 

Mrs.  Willard  is  well  known  throughout  the  country  as  a  lady  of  high  attain 
ments,  who  has  distinguished  herself  as  the  Principal  of  Female  Academies,  that 
have  sent  abroad  some  of  the  most  accomplished  females  of  the  land. 

The  plan  of  the  authoress  is  to  divide  the  time  into  periods,  of  which  the  be- 
ginning and  the  end  are  marked  by  some  important  event,  and  then  care  has 
been  taken  to  make  plain  the  events  of  intermediate  periods.  The  style  is  clear, 
and  there  appears  no  confusion  in  the  narrative.  In  looking  through  the  work, 
we  do  not  discover  that  the  author  has  any  early  prejudices  to  gratify.  The 
book,  therefore,  so  far  as  we  have  been  able  to  judge,  may  be  safely  recom- 
mended as  one  of  great  merit,  and  the  maps  and  marginal  notes,  and  series  of 
questions,  give  additional  value  to  the  work. 

From  the  Xewburyport  Watchman. 

Air  ABRIDGED  HISTORY  or  THE  UNITED  STATES:  By  Emma  Willard. — We 
think  we  are  warranted  in  saying,  that  it  is  better  adapted  to  meet  the  wants  of 
our  schools  and  academies  in  which  history  is  pursued,  than  any  other  work  of 
the  kind  now  before  the  public. 

The  style  is  perspicuous  and  flowing,  and  the  prominent  points  of  our  history  are 
presented  in  such  a  manner  as  to  make  a  deep  and  lasting  impression  on  the  mind. 

We  could  conscientiously  say  much  more  in  praise  of  this  book,  but  must  content 
ourselves  by  heartily  commending  it  to  the  attention  of  those  who  are  anxious 
to  find  a  good  text-book  of  American  history  for  the  use  of  schools. 

From  the  Albany  Evening  Journal. 

WILLARD'S  UNITED  STATES. — This  work  is  well  printed  on  strong  white  paper, 
and  is  bound  in  a  plain  substantial  manner— all-important  requisites  in  a  school- 
book.  The  text  is  prepared  with  equal  skill  and  judgment.  The  memory  of  the 
youthful  student  is  aided  by  a  number  of  spirited  illustrations — by  no  means  un- 
important auxiliaries— while  to  lighten  the  labors  of  the  teacher,  a  series  of  ques- 
tions is  adapted  to  each  chapter.  Nor  is  its  usefulness  limited  to  the  school-room 
As  a  book  of  reference  for  editors,  lawyers,  politicians,  and  others,  where  dates  and 
facts  connected  with  every  important  event  in  American  History  may  be  readily 
found,  this  little  book  is  truly  valuable. 

21 


Wizard's  Series  of  School  Histories  and  Charts. 

WILLARD'S 
UNIVERSAL  HISTORY  IN  PERSPECTIVE, 

ILLUSTRATED    WITH    MAPS   AND    ENGRAVINGS. 


THIS  WORK  IS  ARRANGED  IN  THREE  PARTS,  VIZ  : 

ANCIENT,  MIDDLE,  AND  MODERN  HISTORY. 

1.  ANCIENT  HISTORY   is  divided  into  six  periods — comprising 
events  from  the  Creation,  to  the  Birth  of  our  Saviour. 

2.  MIDDLE  HISTORY,  into  five  periods, — from  the  Christian  Era, 
to  the  Discovery  of  America. 

3.  MODERN  HISTORY,  into  nine  periods, — from  the  Discovery  of 
America,  to  the  present  time.     Each  period  marked  by  some  im- 
portant event  and  illustrated  by  maps  or  engravings. 

The  following  resolution  was  offered  and  adopted  at  a  meeting  of  the  Ward 
School  Teachers'  Association  of  the  City  of  New  York,  January  20th,  1847. 

Resolved,  That  the  Ward  School  Teachers'  Association  of  New  York  con- 
siders Willard's  Universal  History  as  a  book  essentially  adapted  to  the  higher 
classes  of  schools  on  account  of  its  vivacity,  lucidness,  and  intelligent  mode  of 
arrangement,  of  dates  and  questions,  and  that  such  a  work  has  long  been  wanted, 
and  as  such  will  endeavor  to  introduce  it  into  their  respective  schools,  aud 
warmly  recommend  it  to  public  patronage. 


Extract  of  a  Letter  from  Mr.  Elbridge  Smith,  late  Principal  of  the  English 

High  School  of  Worcester,  Mass. 

I  have  recently  introduced  "  Willard's  Universal  History  in  Perspective,"  into 
the  school  under  my  care.  I  am  much  pleased  with  it,  and  think  it  superior  to 
any  other  work  of  the  kind. 

(Signed,) 

ELBRIDGE  SMITH. 
Worcester,  June  5,  1847. 

From  Professor  Charles  B.  Haddock  of  Dartmouth  College,  and  School  Commissioner 

of  the  State  of  New  Hampshire. 

I  am  acquainted  with  Mrs.  Willard's  Histories,  and  entertain  a  high  opinion  of 
them.  They  are  happily  executed,  and  worthy  of  the  long  experience  and  emi- 
nent character  of  their  author. 

(Signed,) 

CHARLES  B.  HADDOCK. 
Dartmouth  College,  Hanover,  Dec.  11,  1846. 

22 


Fulton  <&  Eastman's  Principles  of  Penmanship. 

FULTON  &  EASTMAN'S  PENMANSHIP, 

Illustrated  and  expeditiously  taught  by  the  use  of  a  series  of  Chirographic 
Charts,  a  Key,  and  a  set  of  School  Writing- Books,  appropriately  ruled. 

I. 
CHIROGRAPHIC   CHARTS, 

IN    TWO    NUMBERS.       (Price  5.00.) 

Chart  No.  1,  EMBRACES  PRIMARY  EXERCISES,  AND  ELEMENTARY  PRINCIPLES 

IN  WRITING. 

Chart  No.  2,  EMBRACES  ELEMENTARY  PRINCIPLES  FOR  CAPITALS  COMBINED, 
AND  ELEMENTARY  PRINCIPLES  FOR  SMALL  LETTERS  COM- 
BINED. 

II. 

KEY  TO  CHIROGRAPHIC  CHARTS ; 

Containing  directions  for  the  position  at  the  desk,  and  manner  of  holding 
the  pen. — Also  for  the  exact  forms  and  proportions  of  letters,  with  Rules 
for  their  execution.     (Price  25  cents.) 
III. 

SCHOOL  WRITING-BOOKS. 
IN  FOUR  NUMBERS.     (Price  12$  cents  each.) 

From  the  Trustees  of  the  Union  School,  Lyons,  JV.  Y. 

The  undersigned,  trustees  of  the  Union  District  School  of  the  town  of  Lyons, 
take  this  method  of  expressing  their  approval  of  "  Fulton's  Principles  of  Pen- 
manship." They  have  seen  the  system  in  operation,  during  the  past  year,  in  the 
school  with  which  they  are  connected,  and  are  fully  satisfied  of  its  great  superi- 
ority over  all  other  systems  heretofore  used.  The  "  Chirographic  Charts,"  upon 
which  are  drawn  in  large  size  the  different  letters  and  parts  of  the  letters  of  the 
alphabet,  proportioned  in  accordance  with  the  rules  laid  down  by  the  author  for 
the  formation  of  each  letter,  and  which,  when  suspended,  can  be  seen  from  all 
parts  of  a  school-room  of  ordinary  size,  they  regard  as  an  especial  improvement 
upon,  and  advantage  over,  other  modes  of  teaching  this  art.  While  the  labor  of 
the  teacher  is  by  this  means  lightened  a  hundredfold,  from  the  fact  that  the  direc- 
tions and  rules  thus  illustrated,  can  be  explained  to  a  whole  class  at  once,  the 
benefit  to  the  scholar  is  proportionally  increased.  The  charts  being  made  the 
property  of  the  district,  a  uniformity  is  established  in  this  branch  of  instruction, 
and  the  continual  changes  in  books  and  methods  of  teaching,  which  have  hereto- 
fore given  occasion  to  so  much  just  complaint  on  the  part  of  parents  and  guard- 
ians, and  which  have  been  so  prejudicial  to  the  pupil,  are  entirely  avoided.  * 

The  brief  space  necessarily  allotted  to  a  notice  of  this  kind,  will  not  permit  the 
undersigned  to  say  all  they  might  say  with  truth  in  praise  of  Mr.  F.'s  system  of 
instruction.  They  therefore  conclude  with  the  remark  that  it  meets  their  entire 
approbation,  and  they  cordially  commend  it  to  the  favorable  notice  of  the  friends 
of  education  generally,  and  would  recommend  its  adoption  by  academies  and 
common  schools  in  this  and  in  other  states. 

A.  L.  BEAUMONT 
ELI  JOHNSON, 

Dottd  Lyons,  N.  Y.,  April  5th,  1847.  DE  WITT  PARSHALL, 

25 


Fulton  &  JEastman's  Principles  of  Penmanship. 

NEWARK,  March  3,  1848. 

I  have  examined  with  much  care  Fulton's  System  of  Penmanship,  lately  pub- 
lished by  Messrs.  A.  S.  Barnes  &  Co.,  of  New  York.  My  attention  has  been  called 
to  the  subject  of  teaching  penmanship  in  our  public  schools,  from  the  very  mani- 
fest want  of  any  system  that  seemed  at  all  suited  to  the  character  of  our  Ward 
Schools.  Mr.  Fulton's  system  I  deem  to  be  the  best  I  ever  saw,  and  I  have  no 
hesitation  in  recommending  it.  There  is  an  exactness  about  Mr.  F.'s  method  of 
teaching  this  art,  which  seems  to  defy  the  possibility  of  pupils  becoming  any 
thing  but  accomplished  proficients. 

I  have  taken  means  to  procure  the  introduction  of  one  set  of  the  charts  and  a 
number  of  the  copy-books  in  our  schools  as  an  experiment,  and  so  well  satisfied 
am  I  that  the  system  is  what  we  need,  that  I  shall  use  early  measures  to  have 
them  introduced  more  extensively. 

Yours,  &c.,  JNO.  WHITEHEAD, 

Commissioner  of  Public  Schools  for  the  city  of  Newark 

From  the  Superintendent  oj  Monroe  County,  West  District. 
MR.  LEVI  S.  FULTON: 

Dear  Sir : — I  am  well  pleased  with  the  examination  of  your  series  of  "  Chiro- 
graphic  Charts,  for  the  purpose  of  illustrating  and  teaching  the  principles  of  Pen- 
manship." One  of  the  greatest  obstacles  in  the  way  of  the  scholar's  improve- 
ment in  our  schools,  is  the  frequent  change  of  teachers.  Under  the  instruction 
of  every  new  teacher,  the  scholar  commences  to  learn  a  new  hand,  by  attempting 
to  copy  that  of  the  teacher :  the  consequence  is,  that  he  rarely  obtains  a  good 
permanent  hand.  His  efforts  so  often  failing  of  success,  he  becomes  discouraged, 
Mid  ready  to  abandon  the  exercise  as  a  vexatious  and  hopeless  task. 

By  the  use  of  your  charts,  applying  the  principles  as  taught  in  your  book,  the 
teacher  and  pupil  will  be  very  much  aided  in  the  exercise  ;  the  teacher  illustra- 
ting the  principles  from  the  chart,  and  the  pupil  practising  upon  them. 

I  rejoice  that  you  have  so  arranged  these  principles,  that  the  art  of  good  pen- 
manship will  be  placed  within  the  reach  of  all  who  desire  to  attain  this  necessary 
accomplishment,  and  I  will  indulge  the  hope,  that  your  works  may  obtain  that 
extensive  circulation  which  their  merits  so  richly  deserve. 

Desiring  your  best  success  in  this  praiseworthy  undertaking,  I  shall  ever  re- 
main your  most  obedient  and  humble  servant, 

JULIUS  A.  PERKINS, 
County  Superintendent,  Monroe  co.,  West  District. 

Spencerport,  Dec.  26,  1846. 

LEVI  S.  FULTON,  Esq. : 

Dear  Sir : — Your  theory  and  practice  of  Penmanship,  which  I  have  had  several 
opportunities  to  see  tested  and  applied,  is,  in  my  opinion,  truly  philosophical,  and 
fully  justifies  the  high  estimate  formed  of  it  by  all  to  whom  it  has  been  exhibited. 

I  have  examined  the  plan  of  your  proposed  publication,  and  entirely  approve 
of  it.  It  seems  to  me  that  such  a  work  is  greatly  needed,  and  that  its  adoption  as 
a  text-book  would  greatly  facilitate  the  acquisition  of  a  beautiful  but  hitherto  vex 
atious  branch  of  education. 

REV.  0.  R.  HOWARD,  A.  M., 
(Late)  Principal  of  Fairfield  Academy. 

Lyons,  Dec.  1,  1846. 

PENFIELD,  Jan.  31,  1848. 

Dear  Sirs : — It  is  with  pleasure  I  inform  you  that  your  Chirographic  Charts  aro 
in  use  in  th«  Union  School  of  this  village,  with  admirable  success.  Serious  diffi- 

26 


Fulton  <k  Eastman's  Principles  of  Penmanship. 

culties  which  presented  themselves  to  the  learner  of  writing  by  the  old  system 
(imitation  merely)  are  entirely  overcome. 

The  fixed  rules  for  the  formation  of  each  principle  separately,  and  most  espe- 
cially the  general  arrangement  of  your  Charts,  are  desiderata  hitherto  unreached 
Dy  any  system  of  penmanship  with  which  I  am  acquainted. 

In  my  humble  opinion,  they  must  meet  with  universal  approbation. 

Very  respectfully,  yours,  &c.,  WM.  D.  SHUART. 

MESSRS.  FULTON  &.  EASTMAX  : 

Dear  Sirs :— I  have  carefully  examined  your  Chirographic  Charts  and  Key,  and 
am  pleased  to  find  your  system  of  penmanship  one  that  at  once  recommends  it- 
self by  its  perfection  and  simplicity — requisites  indispensable  to  successful  ap- 
plication in  our  schools,  and  for  a  lack  of  which,  others  have  proved  failures. 
As  teachers  themselves  are  not  unfrequently  inferior  penmen,  and  have  gained 
their  own  knowledge  of  this  branch  of  education  by  a  random  practice,  they  are 
wholly  unable  to  impart  it  to  their  pupils.  Your  system  obviates  this  difficulty, 
by  giving  the  teacher  a  resource  from  which  to  supply  his  own  deficiency,  and 
hints  for  the  successful  application  of  whatever  knowledge  of  the  art  he  may 
possess. 

Your  chart?  are  in  use  in  the  Union  and  Select  schools  of  this  village,  and  also 
in  other  schools  of  this  town  and  county,  and  with  the  happiest  success.  The 
scholars,  charmed  with  the  novelty  which  the  system  continually  presents,  and 
the  ease  with  which  they  master  its  principles,  vie  with  each  other  in  their  efforts 
to  excel,  and  are  rewarded  by  acquiring  a  beautiful  "  hand"  and  neat  mechanical 
execution— and  at  the  same  time,  the  teacher  is  relieved  from  the  perplexing 
practice  of  random  teaching,  so  universal  in  our  schools. 

JAMES  M.  PHINNEY, 
County  Superintendent,  Monroe  Co.,  East  Dist. 

Penfield,  Nov.  1,  1847. 

From  the  Rochester  Monthly  Educator. 

We  believe  that  Mr.  Fulton  is  the  first  author  who  has  attempted  to  teach  the 
Art  of  penmanship  by  rule.  Heretofore,  imitation  has  been  almost  the  sole  princi- 
ple used  to  direct  the  student  in  acquiring  a  knowledge  of  chirography,  and  as 
every  teacher  has  a  system  peculiar  to  himself,  no  uniform  plan  of  instruction 
could  be  successfully  introduced  into  our  common  schools.  Mr.  Fulton  has  ren- 
dered an  essential  service  to  the  cause  of  education,  in  perfecting  a  system  which 
does  not,  at  every  change  of  teacher,  require  a  variation  in  the  handwriting  ot 
the  pupil.  One  advantage  which  must  result  to  the  teacher  from  the  use  of  these 
charts,  is  the  great  amount  of  time  and  labor  that  will  be  saved  thereby — the  old 
method  of  writing  separate  copies  for  each  scholar  being  entirely  dispensed  with 
We  feel  confident  that  teachers  and  parents  who  will  take  time  to  examine  this 
system  of  penmanship  must  be  convinced  of  its  superiority  over  all  others. 

27 


Fulton  &  Eastman's  Book- Keeping. 


FULTON  SL  EASTMAN'S  BOOK-KEEPING. 
A  PRACTICAL  SYSTEM  OF  BOOK-KEEPING  BY  SINGLE  ENTRY' 

Containing  three  distinct  forms  of  books,  adapted  for  the 
Farmer,  Mechanic,  and  Merchant — to  which  is  added  a  va- 
riety of  useful  forms  for  practical  use,  viz. :  Notes,  Bills, 
Drafts,  Receipts,  &c.  &c. :  also  a  Compendium  of  Rules  ot 
Evidence  applicable  to  Books  of  Account,  and  of  Law  in 
reference  to  the  Collection  of  Promissory  Notes,  &c.  By 
LEVI  S.  FULTON  and  G.  W.  EASTMAN,  authors  of  a  complete 
System  of  Penmanship. 

ROCHESTER,  Feb.  12,  1848 
L.  S.  FULTON,  Esq. : 

Dear  Sir : — I  have  examined  with  much  satisfaction  your  System  of  Book-Keep- 
ing, and  take  pleasure  in  recommending  its  adoption  to  my  immediate  friends 
and  others. 

It  is  simple  and  easily  reduced  to  practice,  and  possesses  a  peculiar  adaptation 
to  the  wants  of  the  community  for  which  you  design  it. 

The  plan  for  Merchants'  Books,  which  I  examined  more  critically  than  other 
portions  of  the  work,  is  very  neat,  compact,  and  economical,  and  must  ensure  a 
great  degree  of  accuracy  in  keeping  accounts. 
I  believe  your  work  will  meet  the  present  wants  of  community. 

Very  respectfully,  your  friend,  ELIJAH  BOTTUM, 

Book-keeper  for  John  M.  French  &  Co., 
Rochester,  N.  Y. 


I  have  examined  Messrs.  Fulton  &  Eastman's  "  Practical  System  of  Book- 
Keeping  by  Single  Entry,"  and  am  pleased  with  the  work.  As  a  branch  of  Edu- 
cation, Book-Keeping  is  well  deserving  a  high  estimation  ;  and,  I  will  add,  there 
is  none  of  equal  importance  and  utility  more  generally  neglected,  particularly  in 
our  public  schools. 

The  work  above  alluded  to,  is  plain,  simple,  and  comprehensive,  and  well 
adapted  to  meet  the  wants  of  the  business  community.  In  many  respects  I  deem 
it  superior  to  any  other  work  of  the  kind  with  which  I  am  acquainted.  I  shall 
recommend  it  to  the  schools  under  my  charge. 

JOHN  T.  MACKENZIE, 

Lyons,  May  8, 1848.  Town  Superintendent. 

FULTON  &  EASTMAN'S  BOOK-KEEPINO.— We  had  supposed  that,  in  the  multi- 
plicity of  works  on  Book-Keeping,  hardly  any  thing  valuable  remained  to  be 
suggested  by  later  authors,  should  any  such  present  themselves.  But  we  have 
been  convinced  of  our  short-sightedness  in  examining  the  work  with  the  above 
title,  now  before  us.  The  work  is  principally  designed  for  schools— for  common 
schools — but  should  be, in  the  hands  of  every  Farmer,  Mechanic,  and  Merchant 
in  the  land.  It  opens  with  a  system  of  account-keeping  for  farmers,  followed  by 
one  for  mechanics,  and  this,  in  turn,  by  an  admirable  and  comprehensive  system 
of  mercantile  Book-keeping,  which,  for  its  simplicity,  and  time  and  labor  savir 

28 


Fulton  <&  Eastman's  Book-Keeping. 


properties,  possesses  advantages  over  all  other  systems  with  which  we  are  ac- 
quainted. These  advantages  are  thus  set  forth  by  the  authors  in  their  preface, 
and  an  examination  of  the  work  will  convince  any  man  competent  to  judge,  that 
they  are  not  over-estimated  : 

"  It  [the  system  spoken  of]  saves  more  than  one-third  of  the  time  in  journal- 
izing, and  at  least  three-fourths  of  the  labor  in  posting.  It  requires  but  twelve 
lines  in  the  Ledger  to  post  a  year's  business,  while  in  the  ordinary  way  as  many 
pages  may  be  necessary.  In  settling  with  a  person  at  the  end  of  a  year,  you  have 
only  to  refer  back  to  twelve  places  in  the  Journal  to  show  him  all  the  items  of 
his  account,  whereas  in  the  ordinary  manner  of  keeping  books  you  might  have  to 
refer  to  five  hundred." 

Part  II.  of  the  work,  which  was  prepared  by  a  distinguished  member  of  the 
bar,  comprises  "  rules  of  evidence  and  general  rules  of  law  in  relation  to  bills  of 
exchange,  promissory  and  chattel  notes,  checks,  books  of  account,  &c.,  together 
with  a  large  number  of  forms  useful  to  all  classes  of  business  men  ;  such  as  deeds, 
bonds,  mortgages,  bills  of  sale,  powers  of  attorney,  bills  of  exchange,  notes,  re 
ceipts.  &c. 

This  invaluable  work  contains  232  pages  of  duodecimo,  is  printed  in  the  best 
style  of  Messrs.  A.  S.  Barnes  &  Co.,  of  New  York,  on  an  excellent  quality  of  pa 
per,  and  is  afforded  at  the  very  low  price  of  51)  cents  per  copy.— Wayne  Co.  Whig 

LYONS,  May  8,  1848. 

I  have  examined  "  Fulton  &  Eastman  s  Book-Keeping,"  and  regard  it  as  a  use- 
ful work  on  the  subject  of  which  it  mainly  treats.  Its  methodical  arrangement, 
its  simple  and  ready  modes  of  keeping  accounts,  adapted  to  the  business  of  the 
Farmer,  Mechanic,  or  Merchant  respectively,  and  the  neat  style  in  which  it  is 
executed,  recommend  very  strongly  its  use  in  primary  institutions  of  learning, 
and  especially  in  common  schools.  It  is  to  be  hoped  that  its  general  introduction 
as  a  school-book,  will  cause  the  art  of  Book-keeping  to  be  regarded  as  one  of  the 
indispensable  requisites  of  what  is  termed  a  good  English  education. 

JAMES  C.  SMITH. 

From  the  Albany  Spectator. 

FBLTON  &  EASTMAN'S  BOOK-KEEPING. — New  York  :  A.  S.  Barnes  &  Co., 
1848. 

We  are  very  much  pleased  with  the  design  and  execution  of  this  work.  It  is 
exceedingly  practical ;  .being  by  single  entry,  containing  three  different  forms  ot 
books,  for  the  Farmer,  the  Merchant,  and  Mechanic.  To  these  are  added  notes, 
bills,  drafts,  receipts,  and  a  compendium  of  rules  of  evidence  applicable  to  books 
of  account,  and  of  law  in  reference  to  the  collection  of  promissory  notes.  A 
work  of  such  a  character,  and  of  so  much  practical  value,  speaks  for  itself,  and 
stands  in  need  of  no  commendation  from  us  to  ensure  it  a  large  sale  among  all 
classes. 

29 


Clark's  English  Grammar. 


SCIENCE    OF    THE    ENGLISH    LANGUAGE. 


CLARK'S  NEW  ENGLISH  GRAMMAR. 

A  Practical  Grammar,  in  which  WORDS,  PHRASES,  and  SENTENCES 
are  classified,  according  to  their  offices,  and  their  relation  to 
each  other  :  illustrated  by  a  complete  system  of  Diagrams.  By 
S.  W.  CLARK,  A.  M.  Price  50  cts. 

From  the  Rahway  Register. 

It  is  a  most  capital  work,  and  well  calculated,  if  we  mistake  not,  to  supersede, 
even  in  our  best  schools,  works  of  much  loftier  pretension.  The  peculiarity  of  its 
method  grew  out  of  the  best  practice  of  its  author  (as  he  himself  assures  us  in  its 
preface)  while  engaged  in  communicating  the  science  to  an  adult  class ;  and  his 
success  was  fully  commensurate  with  the  happy  and  philosophic  design  he  lias 
unfolded.  Technicality,  as  technicality,  our  author  unceremoniously  discards,  and 
substitutes  on  the  pupil's  part  rational  practice  in  ascertaining  the  office  of  words  in 
sentences,  rather  than  the  usual  mode  of  perplexing  his  memory  with  their  mere 
names  and  forms. 


From  the  New  York  Tribune. 

"  The  Science  of  the  English  Language — A  Practical  Grammar,  in  which 
Words,  Phrases,  and  Sentences  are  classified  according  to  their  offices  and  their 
relation  to  each  other.  Illustrated  by  a  complete  system  of  Diagrams.  By  S.  W 
Clark,  A.  M.,"  is  a  new  work  which  strikes  us  very  favorably.  Its  deviations  from 
older  books  of  the  kind  are  generally  judicious  and  often  important.  We  wish 
teachers  would  examine  it. 

From  the  Courier  and  Enquirer. 

"  A  Practical  Grammar  of  the  English  Language"  by  S.  W.  Clark,  A.  M.,  has 
just  been  published  by  Barnes  &  Co.  It  is  prepared  upon  a  new  plan,  to  meet  diffi- 
culties which  the  author  has  encountered  in  practical  instruction.  Grammar  and 
the  structure  of  language  are  taught  throughout  by  analysis,  and  in  a  way  which 
renders  their  acquisition  easy  and  satisfactory.  From  the  slight  examination, 
which  is  all  we  have  been  able  to  give  it,  we  are  convinced  it  has  points  of  very 
decided  superiority  over  any  of  the  elementary  works  in  common  use.  We  com- 
mend it  to  the  attention  of  all  who  are  engaged  in  instruction 

From  A-  R.  Simmons,  Ex- Superintendent  of  Bristol. 
MR.  CLARK: 

Dear  Sir : — From  a  thorough  examination  of  your  method  of  teaching  the  Eng 
lish  language,  I  am  prepared  to  give  it  my  unqualified  approbation.  It  is  a  plan 
original  and  beautiful — well  adapted  to  the  capacities  of  learners  of  every  age  and 
stage  of  advancement.  Believing  that  the  introduction  into  our  Common  Schools 
and  Academies  of  a  text-book  on  grammar  containing  your  SYSTEM  and  METHOD 
will  greatly  facilitate  the  acquisition  of  the  science  of  the  English  language,  I  re 
spectfully  suggest  that  it  be  permitted  to  come  before  the  public. 
Respectfully 

Grammar  Teachei 

Bristol,  August  28,  1847  ir  ' 

UNIVERSITY 


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